build: switch helm unit test plugin

Switches the action to use the helm-unittest plugin since it's under
active development and has more recent releases.

Author: dhable

.github/workflows/helm-test.yaml

@@ -28,11 +28,11 @@ jobs:
         uses: azure/setup-helm@v3
         with:
           version: v3.12.0
-        
+
       - name: Install helm-unittest plugin
         run: |
-          helm plugin install https://github.com/quintush/helm-unittest
-        
+          helm plugin install https://github.com/helm-unittest/helm-unittest.git
+
       - name: Run helm-unittest
         run: |
-          helm unittest charts/hdx-oss-v2 
+          helm unittest charts/hdx-oss-v2