Set http proxy default to off for browser

[thegecko]

What it does

With reference to #11911, it was suggested to set the http proxy default setting for browsers to off.

How to test

Open a browser app and confirm the http.proxySupport setting defaults to off. Electron apps should still default to override

Review checklist

• As an author, I have thoroughly tested my changes and carefully followed the review guidelines

Reminder for reviewers

• As a reviewer, I agree to behave in accordance with the review guidelines

[msujew]

I would first like to see whether #12266 fixes the issue for users instead of turning the feature off. I believe as it stands, the feature is kind of fundamentally broken, but my PR should address this.

[thegecko]

I would first like to see whether #12266 fixes the issue for users instead of turning the feature off

I was under the impression this feature makes less sense in the browser version and the proxy is for electron apps. Am I mistaken?

[msujew]

@thegecko It makes a bit less sense in the browser version of Theia, but it's still useful. Ideally, using override (or therefore any other value than off) shouldn't impact the functionality of the application at all. That's what my PR is for.

[thegecko]

Ok, feel free to close this PR :)