tor-browser-bundle-bin: use ffmpeg instead of ffmpeg_3

[dotlambda]

Motivation for this change

#94003 and #120372

Things done

• Tested using sandboxing (nix.useSandbox on NixOS, or option sandbox in nix.conf on non-NixOS linux)
• Built on platform(s)
  • NixOS
  • macOS
  • other Linux distributions
• Tested via one or more NixOS test(s) if existing and applicable for the change (look inside nixos/tests)
• Tested compilation of all pkgs that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review wip"
• Tested execution of all binary files (usually in ./result/bin/)
• Determined the impact on package closure size (by running nix path-info -S before and after)
• Ensured that relevant documentation is up to date
• Fits CONTRIBUTING.md.

[FliegendeWurst]

Using https://senkorasic.com/testmedia/ with pulseaudioSupport enabled:

• WEBM (24fps, VP9+Opus, 1280x720): video + audio works
• MP4 (24fps, H.264+AAC, 1280x720): video + audio works
• HEVC (24fps, H.265+AAC, 1920x1080): audio only (as expected)

Disabling pulseaudioSupport did not affect video playback.

[yoctocell]

On Sun, Apr 25 2021, Robert Schütz wrote: * tor-browser-bundle-bin: use ffmpeg instead of ffmpeg_3

LGTM, video and audio playback works fine.