ci: Clean-up the doc-setup step (#3336)

This cleans up the melos `doc-setup` script a bit, if we're lucky it'll
make the ci build the docs again.

melos.yaml

@@ -55,13 +55,13 @@ scripts:
 
   doc-setup:
     steps:
-      - "echo Checking python version:"
-      - 'python3 --version && (python3 -c "import sys; sys.exit(0 if sys.version_info >= (3,8) else 2)" || (echo  Error: Python 3.8+ is required && exit 1))'
-      - "echo Installing required python modules:"
+      - 'echo Checking python version:'
+      - 'python3 --version && python3 -c "import sys; sys.exit(0 if sys.version_info >= (3,8) else 2)" || (echo "Error: Python 3.8+ is required" && exit 1)'
+      - 'echo Installing required python modules:'
       - 'python3 -m pip install -r "$MELOS_ROOT_PATH/doc/_sphinx/requirements.txt"'
-      - "echo Installing dartdoc_json:"
-      - "dart pub global activate dartdoc_json"
-      - "echo Done."
+      - 'echo Installing dartdoc_json:'
+      - 'dart pub global activate dartdoc_json'
+      - 'echo Done.'
     description: Prepares the environment for documentation development.
 
   doc-build: