[BUG] Restored ability to detect FHIaims geometry file by file extension

Small change to formats.py restores the ability to detect FHIaims geometry.in file by the file extension (.in), as it was in the old io code.

Edit: Sorry for the whitespace things, I realized that my vi automatically removes things like spaces/indention in blank lines. If the indention in the ase files is intentional, I can change this in my merge request.