ci: Fix yq command syntax (#881)

The original CCI version used an older version of yq. The syntax changed and this was missed when ported.

Co-authored-by: Tom Proctor <tomhjp@users.noreply.github.com>

.github/workflows/update-helm-charts-index.yml

@@ -16,7 +16,7 @@ jobs:
         run: |-
           export TAG=${{ github.ref_name }}
           git_tag="${TAG#v}"
-          chart_tag=$(yq r Chart.yaml version)
+          chart_tag=$(yq -r '.version' Chart.yaml)
           if [ "${git_tag}" != "${chart_tag}" ]; then
             echo "chart version (${chart_tag}) did not match git version (${git_tag})"
             exit 1