Remove webview auth code for iOS and Android

[bakulf]

Description

This is dead code. In 2.8.0 we have released the auth in app.

Reference

https://mozilla-hub.atlassian.net/browse/VPN-2206

[codecov-commenter]

Codecov Report

Merging #3502 (9f41dd3) into main (17466b5) will increase coverage by 0.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main    #3502      +/-   ##
==========================================
+ Coverage   51.47%   51.48%   +0.01%     
==========================================
  Files         281      272       -9     
  Lines       15828    15007     -821     
  Branches     5772     5532     -240     
==========================================
- Hits         8148     7727     -421     
+ Misses       6852     6600     -252     
+ Partials      828      680     -148     

Flag	Coverage Δ
functional_tests	10.23% <ø> (ø)
lottie_tests	?
qml_tests	?
unit_tests	75.31% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
src/authenticationlistener.cpp	90.00% <ø> (ø)
src/commands/commandui.cpp	23.10% <ø> (ø)
src/mozillavpn.h	57.81% <ø> (-1.57%)	⬇️
lottie/lib/lottieprivatedocument.cpp	52.94% <0.00%> (-42.30%)	⬇️
lottie/lib/lottieprivatewindow.cpp	38.33% <0.00%> (-38.06%)	⬇️
lottie/lib/lottiestatus.h	59.25% <0.00%> (-5.26%)	⬇️
src/closeeventhandler.cpp	28.84% <0.00%> (-3.30%)	⬇️
src/models/whatsnewmodel.cpp	15.68% <0.00%> (-1.27%)	⬇️
lottie/lib/lottieprivate.cpp	31.19% <0.00%> (-1.21%)	⬇️
... and 49 more

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[bakulf]

@strseb there some taskcluster failures. Can you please tell me if they are connected to my PR or not? and if not how to have them fixed?

[strseb]

This mac runner seems to be busted again. @ahal - I think we had our mac runner stuck once, can you maybe help here again?
Wasm seems to be something about the translations - i can look into that.

[ahal]

Thanks. For some reasons the pool (including the level 3 one) keeps getting into a bad state. Dave House has been getting them unstuck, but it keeps happening..

I'll file another relops JIRA ticket, but I think we're going to have to address the underlying cause here as this is happening much too frequently :/