Branch name should sanitised to match actual github branch name in repository plr list

Description of problem:

Branch name in repository pipelineruns list view should match the actual github branch name.

Version-Release number of selected component (if applicable):

4.11.z

How reproducible:

alwaus

Steps to Reproduce:

1. Create a repository
2. Trigger the pipelineruns by push or pull request event on the github 

Actual results:

Branch name contains "refs-heads-" prefix in front of the actual branch name eg: "refs-heads-cicd-demo" (cicd-demo is the branch name)

Expected results:

Branch name should be the acutal github branch name. just `cicd-demo`should be shown in the branch column.

Additional info:
Ref: https://coreos.slack.com/archives/CHG0KRB7G/p1667564311865459