Bump Firefox Beta to v2.2.0.7921 (beta3)
Bump Firefox Beta to v2.2.0.7921 (beta3)

Release Notes:
https://github.com/ipfs-shipyard/ipfs-companion/releases/tag/v2.2.0beta3

lidel/ipfs-firefox-addon,lidel/ipfs-firefox-addon,lidel/ipfs-firefox-addon