GH Actions: fix use of deprecated set-output

GitHub has deprecated the use of `set-output` (and `set-state`) in favour of new environment files.

This commit updates workflows to use the new methodology.

Refs:
* https://github.blog/changelog/2022-10-11-github-actions-deprecating-save-state-and-set-output-commands/
* https://docs.github.com/en/actions/using-workflows/workflow-commands-for-github-actions#environment-files

Author: jrfnl

.github/workflows/test.yml

@@ -97,11 +97,11 @@ jobs:
           # Set the "short_open_tag" ini to make sure specific conditions are tested.
           # Also turn on error_reporting to ensure all notices are shown.
           if [[ ${{ matrix.custom_ini }} == true && "${{ matrix.php }}" == '5.5' ]]; then
-            echo '::set-output name=PHP_INI::error_reporting=-1, display_errors=On, date.timezone=Australia/Sydney, short_open_tag=On, asp_tags=On'
+            echo 'PHP_INI=error_reporting=-1, display_errors=On, date.timezone=Australia/Sydney, short_open_tag=On, asp_tags=On' >> $GITHUB_OUTPUT
           elif [[ ${{ matrix.custom_ini }} == true && "${{ matrix.php }}" == '7.0' ]]; then
-            echo '::set-output name=PHP_INI::error_reporting=-1, display_errors=On, date.timezone=Australia/Sydney, short_open_tag=On'
+            echo 'PHP_INI=error_reporting=-1, display_errors=On, date.timezone=Australia/Sydney, short_open_tag=On' >> $GITHUB_OUTPUT
           else
-            echo '::set-output name=PHP_INI::error_reporting=-1, display_errors=On'
+            echo 'PHP_INI=error_reporting=-1, display_errors=On' >> $GITHUB_OUTPUT
           fi
 
       - name: Install PHP