Clear playlist if clear flag is set (UpNext)

[CeruleanRed]

• Specifically continue to play the playlist at the insertion index
• Remove what seems to be a left over commented out section

Fixes issues with up next plugin where the popup would not show up after the first episode. Tested with Kodi v21 and jf4k 1.0.3 on Windows 11.

Fixes #717

[sonarcloud[bot]]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
No data about Coverage
0.0% Duplication on New Code

See analysis details on SonarCloud

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 0% with 3 lines in your changes missing coverage. Please review.

Project coverage is 21.49%. Comparing base (1899ecb) to head (91b35cb). Report is 9 commits behind head on master.

Files	Patch %	Lines
jellyfin_kodi/objects/actions.py	0.00%	3 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #871 +/- ## ========================================== - Coverage 21.51% 21.49% -0.02% ========================================== Files 63 63 Lines 8632 8638 +6 Branches 1589 1589 ========================================== Hits 1857 1857 - Misses 6751 6757 +6 Partials 24 24 ```

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[oddstr13]

I don't immediately see any issues, but I'll run it a bit to test.

The commented out line came from the emby version, and has never been uncommented in jf4kodi