ALEInfo no longer lists the enabled fixers, even though they're active

## Information

**VIM version**

```
NVIM v0.5.0
Build type: Release
```

Operating System: arch linux

## What went wrong

Even when `b:ale_fixers` is set, `:ALEInfo` does not show the "Enabled Fixers" section, even though they appear to be working.

## Reproducing the bug

1. Install ale plugin (broken on master and v3.1.0)
1. have an ftplugin (`~/.config/nvim/ftplugin/python.vim`) defining `b:ale_fixers`
1. edit a file

In `~/.config/nvim/ftplugin/python.vim`:
```
let b:ale_linters = ['jedils', 'mypy', 'flake8']
let b:ale_fixers = ['black']
```

### :ALEInfo
```
Current Filetype: python
Available Linters: ['bandit', 'flake8', 'jedils', 'mypy', 'prospector', 'pycodestyle', 'pydocstyle', 'pyflakes', 'pylama', 'pylint', 'pylsp', 'pyre', 'pyright', 'vulture']
Enabled Linters: ['flake8', 'jedils', 'mypy']
Ignored Linters: []
Suggested Fixers:
'add_blank_lines_for_python_control_statements' - Add blank lines before control statements.
'autoimport' - Fix import issues with autoimport.
'autopep8' - Fix PEP8 issues with autopep8.
'black' - Fix PEP8 issues with black.
'isort' - Sort Python imports with isort.
'remove_trailing_lines' - Remove all blank lines at the end of a file.
'reorder-python-imports' - Sort Python imports with reorder-python-imports.
'trim_whitespace' - Remove all trailing whitespace characters at the end of every line.
'yapf' - Fix Python files with yapf.
Linter Variables:

let g:ale_python_auto_pipenv = 0
let g:ale_python_flake8_auto_pipenv = 0
let g:ale_python_flake8_change_directory = 'project'
let g:ale_python_flake8_executable = 'flake8'
let g:ale_python_flake8_options = ''
let g:ale_python_flake8_use_global = 0
let g:ale_python_jedils_auto_pipenv = 0
let g:ale_python_jedils_executable = 'jedi-language-server'
let g:ale_python_jedils_use_global = 0
let g:ale_python_mypy_auto_pipenv = 0
let g:ale_python_mypy_executable = 'mypy'
let g:ale_python_mypy_ignore_invalid_syntax = 0
let g:ale_python_mypy_options = ''
let g:ale_python_mypy_show_notes = 1
let g:ale_python_mypy_use_global = 0
Global Variables:

let g:ale_cache_executable_check_failures = v:null
let g:ale_change_sign_column_color = 0
let g:ale_command_wrapper = ''
let g:ale_completion_delay = 100
let g:ale_completion_enabled = 1
let g:ale_completion_max_suggestions = 50
let g:ale_disable_lsp = 0
let g:ale_echo_cursor = 1
let g:ale_echo_msg_error_str = 'Error'
let g:ale_echo_msg_format = '%code: %%s'
let g:ale_echo_msg_info_str = 'Info'
let g:ale_echo_msg_warning_str = 'Warning'
let g:ale_enabled = 1
let g:ale_fix_on_save = 1
let g:ale_fixers = {'*': ['remove_trailing_lines', 'trim_whitespace']}
let b:ale_fixers = ['black']
let g:ale_history_enabled = 1
let g:ale_history_log_output = 1
let g:ale_keep_list_window_open = 0
let g:ale_lint_delay = 200
let g:ale_lint_on_enter = 1
let g:ale_lint_on_filetype_changed = 1
let g:ale_lint_on_insert_leave = 1
let g:ale_lint_on_save = 1
let g:ale_lint_on_text_changed = 'normal'
let g:ale_linter_aliases = {}
let g:ale_linters = {}
let b:ale_linters = ['jedils', 'mypy', 'flake8']
let g:ale_linters_explicit = 0
let g:ale_linters_ignore = {}
let g:ale_list_vertical = 0
let g:ale_list_window_size = 10
let g:ale_loclist_msg_format = '%code: %%s'
let g:ale_max_buffer_history_size = 20
let g:ale_max_signs = -1
let g:ale_maximum_file_size = v:null
let g:ale_open_list = 0
let g:ale_pattern_options = v:null
let g:ale_pattern_options_enabled = v:null
let g:ale_root = {}
let g:ale_set_balloons = 0
let g:ale_set_highlights = 1
let g:ale_set_loclist = 1
let g:ale_set_quickfix = 0
let g:ale_set_signs = 1
let g:ale_sign_column_always = 0
let g:ale_sign_error = '>>'
let g:ale_sign_info = '--'
let g:ale_sign_offset = 1000000
let g:ale_sign_style_error = '>>'
let g:ale_sign_style_warning = '--'
let g:ale_sign_warning = '--'
let g:ale_sign_highlight_linenrs = 0
let g:ale_statusline_format = v:null
let g:ale_type_map = {}
let g:ale_use_global_executables = v:null
let g:ale_virtualtext_cursor = 0
let g:ale_warn_about_trailing_blank_lines = 1
let g:ale_warn_about_trailing_whitespace = 1
Command History:

(executable check - success) flake8
(finished - exit code 0) ['/bin/zsh', '-c', 'cd ''/home/jeremy/example'' && ''flake8'' --version']

<<>>
3.9.2 (mccabe: 0.6.1, pycodestyle: 2.7.0, pyflakes: 2.3.1) CPython 3.9.6 on
Linux
<<>>

(executable check - success) jedi-language-server
(executable check - success) mypy
(finished - exit code 0) ['/bin/zsh', '-c', 'cd ''/home/jeremy/example'' && ''mypy'' --show-column-numbers --shadow-file ''/home/jeremy/example/test.py'' ''/home/jeremy/.local/tmp/nvimy3QAbq/3/test.py'' ''/home/jeremy/example/test.py''']

<<>>
Success: no issues found in 1 source file
<<>>

(finished - exit code 1) ['/bin/zsh', '-c', 'cd ''/home/jeremy/example'' && ''flake8'' --format=default --stdin-display-name ''/home/jeremy/example/test.py'' - < ''/home/jeremy/.local/tmp/nvimy3QAbq/4/test.py''']

<<>>
/home/jeremy/example/test.py:1:1: F401 'sys' imported but unused
<<>>

(started) ['/bin/zsh', '-c', '''jedi-language-server''']
```