Add dgoulet's obfs4 bridge to Tor Browser's default bridges

After the suggestion to remove #19714 (closed), dgoulet offered an obfs4 bridge as a default TB obfs4 bridge. The other obfs4 bridge operators have told me their bridges are saturated, so, provided that dgoulet's bridge can provide bandwidth similar to the others (see #18113 (moved) for how the round robining doesn't yet take bandwidth into account) then I propose we add it.

@dgoulet Could we get the bridge line for it privately (so that dcf can continue to run tests on how things are blocked)? Or, if you feel like it, you can patch it into Bundle-Data/PTConfigs/bridge_prefs.js in the tor-browser-bundle repo, and give one of the TB team the patch.