ubuntu.yml in html2doc-0.9.4

- old
+ new

@@ -1,9 +1,13 @@
 # Auto-generated !!! Do not edit it manually
 # use ci-master https://github.com/metanorma/metanorma-build-scripts
 name: ubuntu
 
-on: [push, pull_request]
+on:
+  push:
+    branches: [ master ]
+  pull_request:
+    branches: [ '**' ]
 
 jobs:
   test-linux:
     name: Test on Ruby ${{ matrix.ruby }} Ubuntu
     runs-on: ubuntu-latest