ci: chekcout helm doc action before using it

Signed-off-by: Emilien Escalle <emilien.escalle@escemi.com>

Author: neilime

.github/workflows/__main-ci.yml

@@ -57,6 +57,8 @@ jobs:
     if: github.event_name != 'schedule'
     runs-on: ubuntu-latest
     steps:
+      - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
+
       - uses: ./actions/helm/generate-docs
         with:
           working-directory: ./tests/charts