Add extra space before optional contextily package

Xref #2536 (comment)

Author: weiji14

.github/workflows/ci_tests.yaml

@@ -67,8 +67,8 @@ jobs:
             optional-packages: ''
           - python-version: '3.11'
             numpy-version: '1.24'
-            optional-packages: |
-              contextily
+            optional-packages: >-
+               contextily
               geopandas
               ipython
               rioxarray