Fix typo in GitHub action

.github/workflows/build-docs.yml

@@ -32,7 +32,7 @@ jobs:
       - name: Checkout
         uses: actions/checkout@v3
       - name: Set up Python
-        uses: actions/setup-=python@v2
+        uses: actions/setup-python@v2
         with:
           python-version: 3.9
       - name: Install documentation build dependencies