Restrict badge to only include push (PR merge) events

Author: jsiirola

README.md

@@ -1,4 +1,4 @@
-[![GitHub Actions Status](https://github.com/Pyomo/pyomo/actions/workflows/test_pr_and_main.yml/badge.svg?branch=main)](https://github.com/Pyomo/pyomo/actions/workflows/test_pr_and_main.yml?query=event%3Apush)
+[![GitHub Actions Status](https://github.com/Pyomo/pyomo/actions/workflows/test_pr_and_main.yml/badge.svg?branch=main&event=push)](https://github.com/Pyomo/pyomo/actions/workflows/test_pr_and_main.yml?query=branch%3Amain+event%3Apush)
 [![Jenkins Status](https://github.com/Pyomo/jenkins-status/blob/main/pyomo_main.svg)](https://pyomo-jenkins.sandia.gov/)
 [![codecov](https://codecov.io/gh/Pyomo/pyomo/branch/main/graph/badge.svg)](https://codecov.io/gh/Pyomo/pyomo)
 [![Documentation Status](https://readthedocs.org/projects/pyomo/badge/?version=latest)](http://pyomo.readthedocs.org/en/latest/)