Fenix: FNX3-16956 ⁃ Remove AMO/SUMO workaround for GeckoView 68

[jonalmeida]

For #1134 we're putting in a change to update our user-agent on those sites while we're still on GV 68. This should be removed when we upgrade to GV 69.

[bifleming]

@st3fan @cpeterso is this the solution we want?

[cpeterso]

is this the solution we want?

Yes. This issue asks to remove a temporary workaround that is only needed for "Fenix 68". This issue can be fixed after Fenix updates to GV 69 or later.

[jonalmeida]

We can do this now that https://github.com/mozilla-mobile/fenix/pull/4297 has landed!

What needs to be done:

• Remove the UserAgentRewriter.
• Remove all it's usages.

This is the PR that added the change (which now needs to be removed): https://github.com/mozilla-mobile/fenix/pull/3342/

[jonalmeida]

For QA: Testing this would be to open addons.mozilla.org and verify that addons _cannot_ be installed on Fenix.

[sv-ohorvath]

Verified as fixed on Nightly 190806, GV 69.