master -> main: github now defaults to "main", s2i to "master"

Description of problem:

On the Builds editing screen, it does not have a place for git ref, which is assumed to be "master" via the Add from Git (s2i) UI.  This is particularly tricky when adding a github webhook to the repository since it fires and receives a 200 but the build does not trigger.

Builds UI missing git ref

https://www.screencast.com/t/GyGiiY4Qv

work around is to edit the yaml directly

or to add the "main" git ref when initially using the Add from Git UI

https://www.screencast.com/t/I0U6gmHB

Prerequisites (if any, like setup, operators/versions):

Steps to Reproduce

1. Fork https://github.com/2percentsilk/haikus-for-codespaces
2. Add From Git https://github.com/burrsutter/nodecodespaces
3. Fix the Service to point to port 3000
4. Go to Builds and copy the Webhook https://www.screencast.com/t/Nw0uLrnfTGe
5. Add to the github repo (pick content-type:json) https://github.com/burrsutter/nodecodespaces/settings/hooks
6. Edit the code on github by hitting "." period https://www.screencast.com/t/JNUpwCLBY
7. Save and commit
8. and the Build does not execute because the github repo is set to "main" branch and Add From Git/S2I assumes "master" and that UI bit is missing from the Build screen, making this tricky to figure out (and there is no error message back to the webhook)

Actual results:

Expected results:

Reproducibility (Always/Intermittent/Only Once): Always

Build Details:

Additional info: