CI: consider using black-only for format checking

[karlch]

After merging #660, I noticed that black (in my pre-commit) still produced a diff, although pylint did not complain.

For consistency, it would be better to only use black for formatting, and disable all related pylint checks and possibly even remove pycodestyle.

Useful command:

black --check --diff

Sample output:

@@ -323,11 +323,11 @@

     ORDER_TYPES: Dict[str, Callable[..., Any]] = {
         "alphabetical": str,
         "natural": natural_sort,
         "recently-modified": os.path.getmtime,
-        "none": lambda x: 0
+        "none": lambda x: 0,
     }

     STR_ORDER_TYPES = "alphabetical", "natural"

     def __init__(
@@ -471,11 +471,11 @@

     size = ThumbnailSizeSetting("thumbnail.size", 128, desc="Size of thumbnails")
     save = BoolSetting(
         "thumbnail.save",
         True,
-        desc="Save new thumbnails to the disk in the shared icon cache for later use"
+        desc="Save new thumbnails to the disk in the shared icon cache for later use",
     )


 class slideshow:  # pylint: disable=invalid-name
     """Namespace for slideshow related settings."""
would reformat ~/Coding/VimivQt/vimiv/api/settings.py

Oh no! 💥 💔 💥
1 file would be reformatted, 92 files would be left unchanged.