update type hints for better Python compatibility - #560

argcomplete/completers.py:37:46: FA100 Add `from __future__ import annotations` to simplify `typing.Union` help: Add `from __future__ import annotations`

argcomplete/completers.py:37:33: FA102 Missing `from __future__ import annotations`, but uses PEP 585 collection help: Add `from __future__ import annotations`

argcomplete/completers.py:35:33: FA100 Add `from __future__ import annotations` to simplify `typing.Union` help: Add `from __future__ import annotations`

argcomplete/completers.py:35:20: FA102 Missing `from __future__ import annotations`, but uses PEP 585 collection help: Add `from __future__ import annotations`

argcomplete/completers.py:30:10: FA102 Missing `from __future__ import annotations`, but uses PEP 585 collection help: Add `from __future__ import annotations`

argcomplete/_check_module.py:57:14: SIM115 Use a context manager for opening files

argcomplete/_check_module.py:34:45: UP032 Use f-string instead of `format` call help: Convert to f-string

argcomplete/_check_module.py:29:41: UP032 Use f-string instead of `format` call help: Convert to f-string

argcomplete/_check_console_script.py:51:8: UP032 Use f-string instead of `format` call help: Convert to f-string