Use master composer action

Author: Greg Bowler

.github/workflows/ci.yml

@@ -8,7 +8,7 @@ jobs:
 
     steps:
       - uses: actions/checkout@v2
-      - uses: php-actions/composer@v3
+      - uses: php-actions/composer@master
       - name: PHPUnit Tests
         uses: php-actions/phpunit@17-php-versions
         with: