BUG: List of files in `find_files_in_dir()` shows up in `find_files()`

after using `find_files_in_dir` (the directory being `vim.fn.stdpath("config")` in my case), the same files show up in `find_files` even if i am not in `vim.fn.stdpath("config")`.

steps to reproduce:
1. open project different from directory in `find_files_in_dir`
2. use `find_files_in_dir`
3. files from step 2 are now gonna show up in `find_files` until nvim gets restarted.

Reproduce the issue with the three listed steps, using a project separate from vim.fn.stdpath("config"). Then trace the find_files_in_dir() and find_files() entry points to see how their file lists are retained. Done means files returned by find_files_in_dir() no longer appear in find_files() after switching projects, without requiring a Neovim restart.

Written by the indexing model from the issue text.