Fix the version string for PEP440, and some Qt6 enum accesses

[ferdnyc]

This PR addresses two issues I encountered attempting to install and run videomorph from the repo sources:

1. The version string 1.5-canelo doesn't conform to PEP440, and is therefore invalid. pip install will abort with a traceback due to a packaging.version.InvalidVersion exception. But, 1.5+canelo is perfectly valid, so use that instead.
2. Some enum accesses were still relying on PyQt5 compatibility symbols that are no longer present in PyQt6. Little things like: Edit trigger names are now members of QAbstractItemView.EditTrigger instead of QAbstractItemView; Model roles are now members of Qt.ItemDataRole; The QMessageBox "OK" button is now found at QMessageBox.StandardButton.Ok.

I can't promise I got all of the enum access issues, in the second commit, there could be more. I addressed only the ones I either personally experienced, or saw were guilty of the same issue that caused problems for me.

Also, NOT addressed in this PR is another crash I hit in the converter, specifically in converter.reader.OutputReader.bitrate due to an IndexError:

Traceback (most recent call last):
  File ".../videomorph/forms/videomorph.py", line 1140, in _ready_read
    self._update_conversion_progress()
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^
  File ".../videomorph/forms/videomorph.py", line 1178, in _update_conversion_progress
    self._update_status_bar()
    ~~~~~~~~~~~~~~~~~~~~~~~^^
  File ".../videomorph/forms/videomorph.py", line 1221, in _update_status_bar
    br=self.library.reader.bitrate,
       ^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File ".../videomorph/converter/reader.py", line 63, in bitrate
    return bitrate_read[0].split("=")[-1].strip()
           ~~~~~~~~~~~~^^^
IndexError: list index out of range
[1]    3239129 IOT instruction (core dumped)  videomorph

So, it looks like additional defensive coding and sanity checks are needed there.

[ferdnyc]

Oh, and let me know if I should target the develop branch instead. (Though, if so, it would be good to set that branch as the repo's default branch so all PRs are automatically targeted there.)