CI:website: allow failure (#433)

There are not always necessary documentation updates
to be build and published on `pages` branch

Otherwise we could create an empty commit with
`--allow-empty` Mike option, but we do not want empty traffic
drawback: documentation build could really fail and could be unnoticed

.gitlab-ci.yml

@@ -228,6 +228,7 @@ website:
   stage: website
   needs: ["tests:3.12:cov"]
   extends: .mkdocs_changes
+  allow_failure: true
   variables:
     RELEASE: "0.12"
   rules: