GH Actions: always quote variables

... to satisfy shellcheck rule SC2086: "Double quote to prevent globbing and word splitting".

Ref: https://www.shellcheck.net/wiki/SC2086

Author: jrfnl

.github/workflows/test.yml

@@ -101,9 +101,9 @@ jobs:
         id: set_ini
         run: |
           if [[ "${{ matrix.dependencies }}" != "dev" ]]; then
-            echo 'PHP_INI=error_reporting=E_ALL & ~E_DEPRECATED, display_errors=On' >> $GITHUB_OUTPUT
+            echo 'PHP_INI=error_reporting=E_ALL & ~E_DEPRECATED, display_errors=On' >> "$GITHUB_OUTPUT"
           else
-            echo 'PHP_INI=error_reporting=-1, display_errors=On' >> $GITHUB_OUTPUT
+            echo 'PHP_INI=error_reporting=-1, display_errors=On' >> "$GITHUB_OUTPUT"
           fi
 
       - name: Install PHP