ci: incorrect wording in workflow stage

Author: spwoodcock

.github/workflows/build_mkdocs_img.yml

@@ -4,7 +4,7 @@ on:
   workflow_dispatch:
 
 jobs:
-  build-odkcentral:
+  build-mkdocs:
     uses: hotosm/gh-workflows/.github/workflows/image_build.yml@3.4.3
     with:
       image_name: ghcr.io/${{ github.repository }}/mkdocs