fix: Use 1.9 for doc build

.github/workflows/CI.yml

@@ -152,7 +152,7 @@ jobs:
       - uses: actions/checkout@v4
       - uses: julia-actions/setup-julia@v1
         with:
-          version: '1'
+          version: '1.9'
       - uses: julia-actions/cache@v1
       - name: Configure doc environment
         shell: julia --project=docs --color=yes {0}