Make the Web IDE Beta the default for Self-managed

Problem to solve

On December 19th, we made the Web IDE Beta available, and enabled by default, for all users of GitLab.com. Self-managed users have access to the same functionality but it remains behind a feature flag and is disabled by default. This decision was made to reduce the breadth of impact to self-managed instances if some early bug reports indicated instability or significant usability concerns.

Now that we have been using the Web IDE Beta for almost 2 months, and less than 2% of the active Web IDE users have opted out of the beta, we can move forward with making it enabled by default for all self-managed instances.

Proposal

Enable the Web IDE Beta for all self-managed instances in %15.10.

Default vscode-web-ide to true.