Merge pull request #420 from cclauss/patch-1

Upgrade GitHub Action to v3

Author: isuruf

.github/workflows/ci.yml

@@ -122,7 +122,7 @@ jobs:
 
     steps:
     - name: Checkout code
-      uses: actions/checkout@v2
+      uses: actions/checkout@v3
 
     - name: Build and test symengine
       shell: bash