Bash autocompletion error

Start a new terminal emulator running bash with autocompletion enabled. Type `jupyter note`, you will get:

```
Error executing Jupyter command 'baseopts': [Errno 2] No such file or directory
```

The problem is here:

```
if [ -z "$__jupyter_complete_baseopts" ]; then
_jupyter_get_flags baseopts
__jupyter_complete_baseopts="${opts}"
fi
local baseopts="$__jupyter_complete_baseopts"
```

since `baseopts` is not a subcommand at all! As a workaround one can initialize `__jupyter_complete_baseopts=" "`, but the above code should be removed altogether anyway.

Start at the Bash autocompletion entry point containing the _jupyter_get_flags baseopts block shown in the issue. Reproduce `jupyter note` in a Bash terminal, remove the obsolete baseopts handling, and verify that completion no longer reports the Jupyter `baseopts` command error.

Written by the indexing model from the issue text.