GH-82874: Use f-strings instead of str.format within importlib.__init__.py

[achhina]

Continuation of GH-82874 for importlib.__init__.py.

[methane]

Closing this because massive conflicts and importlib/__init__.py already uses f-string.

[achhina]

Closing this because massive conflicts and importlib/__init__.py already uses f-string.

Ah yes, forgot this was still open, thank you for noticing and closing this. At the time I opened this PR, there weren't any conflicts and importlib's init had not yet fully used f-strings, but I suppose another PR must have addressed that since then.