Upgrade version of pysubs2 (add-on crashes on systems with Python 3.8 or higher)

[IllDepence]

On systems with Python 3.8 or higher the add-on crashes because the version of pysubs2 shipped with the add-on

1. tries to import MutableSequence from collections instead of collections.abc (pysubs2/ssafile.py, line 1)
2. tries to compile a regex with inline global modifiers not positioned at the start of the pattern (pysubs2/mpl2.py, line 9)

Both of these have been fixed in pysubs2 (here and here) since 2021. Going by these commits, the oldest version fixing the problem appears to be 1.3.0, but I guess it wouldn’t hurt to simply ship the most recent version (currently 1.6.1) with the add-on.

Hot fix for anyone with the same problem: I’m on Anki version ⁨2.1.62 (77dd1dc1)⁩ with Python 3.11.2 Qt 6.5.0 PyQt 6.5.0 and manually adjusting above two lines in the pysubs2 code fixed the crash.