ci: add missing analytics token to workflow

Author: purpleclay

.github/workflows/docs.yml

@@ -72,6 +72,7 @@ jobs:
         run: mkdocs build
         env:
           GH_TOKEN: ${{ secrets.GH_MKDOCS }}
+          GH_GOOGLE_ANALYTICS_KEY: ${{ secrets.GH_GOOGLE_ANALYTICS_KEY }}
 
       - name: HTML Test
         uses: wjdp/htmltest-action@master
@@ -83,7 +84,7 @@ jobs:
         if: startsWith(github.ref, 'refs/tags/v')
         env:
           GH_TOKEN: ${{ secrets.GH_MKDOCS }}
-          GOOGLE_ANALYTICS_KEY: ${{ secrets.GH_GOOGLE_ANALYTICS_KEY }}
+          GH_GOOGLE_ANALYTICS_KEY: ${{ secrets.GH_GOOGLE_ANALYTICS_KEY }}
         run: |
           mkdocs gh-deploy --force
           mkdocs --version