docs: Remove Gitter

[panekj]

Remove Gitter (which is now hosted on Matrix) since it's been abandoned for way too long

[github-actions]

🦙 MegaLinter status: ✅ SUCCESS

Descriptor	Linter	Files	Fixed	Errors	Elapsed time
✅ EDITORCONFIG	editorconfig-checker	1		0	0.0s
✅ MARKDOWN	markdownlint	1		0	0.35s
✅ REPOSITORY	gitleaks	yes		no	2.72s
✅ REPOSITORY	git_diff	yes		no	0.01s
✅ REPOSITORY	grype	yes		no	9.45s
✅ REPOSITORY	secretlint	yes		no	1.21s
✅ REPOSITORY	trivy-sbom	yes		no	0.39s
✅ REPOSITORY	trufflehog	yes		no	3.8s

See detailed report in MegaLinter reports
Set VALIDATE_ALL_CODEBASE: true in mega-linter.yml to validate all sources, not only the diff

[ChristopherHX]

...this is one gitter leftover, there is one in issue templates as well

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 74.32%. Comparing base (5a80a04) to head (a8f8d62).
Report is 176 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff             @@
##           master    #2678       +/-   ##
===========================================
+ Coverage   61.56%   74.32%   +12.76%     
===========================================
  Files          53       72       +19     
  Lines        9002    11050     +2048     
===========================================
+ Hits         5542     8213     +2671     
+ Misses       3020     2203      -817     
- Partials      440      634      +194     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.