update code to reflect the new minimum python version 3.7

- update string format method
- remove redundant default arguments from function  calls
- remove unused imports
- remove unicode identifier from strings, it's default in py3 (see: https://stackoverflow.com/a/4182635/12201331)

allianceauth/eveonline/evelinks/evewho.py

@@ -31,7 +31,7 @@ def _build_url(category: str, eve_id: int) -> str:
 
     url = urljoin(
         _BASE_URL,
-        '{}/{}'.format(partial, int(eve_id))
+        f'{partial}/{int(eve_id)}'
     )
     return url