Change service connection

[missymessa]

Summary of the changes

Updated the service connection in AzDO used for DartLabTemplates.

Fixes: Part of work for this issue: https://dev.azure.com/dnceng/internal/_workitems/edit/10123

Team: let me know how I can best test this change

[davidwengier]

To test this change:

• Push your branch to this repo (not your fork)
• Push your branch to https://dnceng.visualstudio.com/internal/_git/dotnet-razor
• Run https://devdiv.visualstudio.com/DevDiv/_build?definitionId=15591&_a=summary and select your branch

Yes you really have to push to two different remotes :)

[missymessa]

@davidwengier I seem to lack push permissions for dotnet/razor. Let me know when I get perms and I'll push it here :)

[davidwengier]

I don't have permission to give you permission, but I can clone your fork and push a couple of branches :)

Test run at: https://devdiv.visualstudio.com/DevDiv/_build/results?buildId=13616692&view=results

[davidwengier]

@missymessa are you happy for me to merge this when the run is finished? I don't expect the tests to 100% pass, but that's hardly the fault of this change. In fact I suspect we're past the point of validating this change already.

[missymessa]

@davidwengier yup, the new service connection exists, I just wanted to make sure it worked for y'all :)