Update build_docs.yml (#423)

main branch is called master not main here

Author: bwheelz36

.github/workflows/build_docs.yml

@@ -3,7 +3,7 @@ name: build docs
 on:
   push:
     branches:
-      - main
+      - master
   pull_request:
 
 jobs:
@@ -41,4 +41,4 @@ jobs:
         if: ${{ github.ref == 'refs/heads/main' }}
         with:
           github_token: ${{ secrets.GITHUB_TOKEN }}
-          publish_dir: ./docs
+          publish_dir: ./docs