ci(chart-test): specify version for helm-unittest plugin

Author: freeznet

.github/workflows/chart-test.yml

@@ -63,7 +63,7 @@ jobs:
 
       - name: Install plugin unittest
         run: |
-          helm plugin install https://github.com/helm-unittest/helm-unittest
+          helm plugin install https://github.com/helm-unittest/helm-unittest --version 1.0.3
 
       # Python is required because `ct lint` runs Yamale (https://github.com/23andMe/Yamale) and
       # yamllint (https://github.com/adrienverge/yamllint) which require Python