[Backport release-24.11] electron_33-bin: mark as insecure because it's EOL, electron-source.electron_33: remove as it's EOL

[nixpkgs-ci]

Bot-based backport to release-24.11, triggered by a label in #397918.

• Before merging, ensure that this backport is acceptable for the release.
  • Even as a non-committer, if you find that it is not acceptable, leave a comment.

[teutat3s]

Affected packages on 24.11 by this change:

• webcord [24.11] webcord: 4.10.3 -> 4.10.5 #406704
• ytmdesktop [24.11] ytmdesktop: 2.0.6 -> 2.0.8, build from source #406985
• bitwarden-desktop [Backport release-24.11] bitwarden-desktop: 2025.1.1 -> 2025.2.0 #406700
• appium-inspector [Backport release-24.11] appium-inspector: 2024.12.1 -> 2025.3.1 #407296
• teams-for-linux [24.11] teams-for-linux: 1.12.7 -> 1.13.1 #406703
• feishin [24.11] feishin: 0.12.2 -> 0.12.6 #406986

[teutat3s]

With #406425 merged we're now building 4 electron versions from source for nixos-24.11. We want to build a maximum of 3 versions from source. I'd like to get this PR merged rather sooner than later and handle the linked PRs with version bumps as a follow up.