bump composer-install action to v3 (#113)

Author: akondas

.github/workflows/tests.yml

@@ -28,7 +28,7 @@ jobs:
         ini-values: memory_limit=-1
 
     - name: "Install composer dependencies"
-      uses: "ramsey/composer-install@v2"
+      uses: "ramsey/composer-install@v3"
 
     - name: "Run test suite"
       run: "composer tests"