Use main branch for helm/chart-releaser-action (#70)

It seems helm has renamed their HEAD from master to main. Update the
github workflow to reflect that.

Fixes #69

Author: Merovius

.github/workflows/helmchart-release.yml

@@ -17,7 +17,7 @@ jobs:
           git config user.email "[email protected]"
 
       - name: Run chart-releaser
-        uses: helm/chart-releaser-action@master
+        uses: helm/chart-releaser-action@main
         with:
           charts_dir: charts
         env: