Change directory to inside checked out repo (ros-navigation#3493)

or relative path under $GITHUB_WORKSPACE that actions/checkout places the repository

Author: ruffsl

.github/workflows/update_ci_image.yaml

@@ -27,6 +27,7 @@ jobs:
  id: check
  if: github.event_name == 'push'
  run: |
+ cd navigation2
  version=$(grep -oP '(?<=<version>).*?(?=</version>)' navigation2/package.xml)
  echo "version=${version}" >> $GITHUB_OUTPUT
  echo "trigger=true" >> $GITHUB_OUTPUT