Change branch name from 'master' to 'main' in workflow

Author: chrisjonesBSU

.github/workflows/pytest.yml

@@ -2,13 +2,13 @@ name: pytest
 
 on:
   push:
-    branches: [ master ]
+    branches: [ main ]
     paths:
       - morphct/**
       - environment.yml
       - .github/workflows/pytest.yml
   pull_request:
-    branches: [ master ]
+    branches: [ main ]
     paths:
       - morphct/**
       - environment.yml