use ubuntu-20.04 for js CI

Author: bollwyvl

.github/workflows/tests.yml

@@ -36,7 +36,8 @@ jobs:
         python -m sphinx -T -E -b html -d ../build/doctrees -D language=en . ../build/html
   js:
     name: JavaScript
-    runs-on: ubuntu-latest
+    # as of #3653 ubuntu-latest wasn't working
+    runs-on: ubuntu-20.04
 
     steps:
     - uses: actions/checkout@v2