chore(dev-launcher) - Change the default context to oauth_webchannel_v1

[jonalmeida]

Because

• This is the default flow that we use in desktop today, but we can't remove the old flow until ESR is updated to v140+.

This pull request

• Changes the default context to use the Firefox browser default OAuth flow.

Issue that this pull request solves

Closes: Fixes FXA-9872

Checklist

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• My commit is GPG signed.
• If applicable, I have modified or added tests which pass locally.
• I have added necessary documentation (if appropriate).
• I have verified that my changes render correctly in RTL (if appropriate).

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Other information (Optional)

From this comment in JIRA:
Following up on #17274, we might want to take this opportunity to clean up the profile for dev-launcher. A lot of the custom configuration might not be needed anymore with the addition of the autoConfig setting.

We still need to support the older flow until the next ESR version (v140), so I don't recommend removing or cleaning up the previous one until the June release.

[LZoog]

We still need to support the older flow until the next ESR version (v140), so I don't recommend removing or cleaning up the previous one until the June release.

@jonalmeida this is just calling out that we don't need all those CONFIGS. I think all we need is identity.fxaccounts.autoconfig.uri?

[jonalmeida]

@LZoog funny enough that in bug 1942925, it was dev-launcher settings those prefs that helped verify that the autoconfig pref wasn't working correctly. 😄

I can remove them too if you feel strongly.

[LZoog]

@jonalmeida if it helped debug something, I say leave it! Maybe we add a comment somewhere noting that?

[jonalmeida]

if it helped debug something, I say leave it! Maybe we add a comment somewhere noting that?

Will do before landing!

Thanks @vbudhram for approving - sorry, I didn't see that earlier!