ci/docs: Always expose the built docs.

When testing my docs changes outside of an MR, there was no way to look at
the result.

Acked-by: Erik Faye-Lund <erik.faye-lund@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/19733>

.gitlab-ci.yml

@@ -135,6 +135,10 @@ stages:
   extends:
     - .fdo.ci-fairy
     - .build-rules
+  artifacts:
+    expose_as: 'Documentation preview'
+    paths:
+    - public/
   script:
   - apk --no-cache add graphviz doxygen
   - pip3 install sphinx===5.1.1 breathe===4.34.0 mako===1.2.3 sphinx_rtd_theme===1.0.0
@@ -144,9 +148,6 @@ stages:
 pages:
   extends: .docs-base
   stage: deploy
-  artifacts:
-    paths:
-    - public
   needs: []
   rules:
     - !reference [.no_scheduled_pipelines-rules, rules]
@@ -175,10 +176,6 @@ test-docs-mr:
     - test-docs
   needs:
     - sanity
-  artifacts:
-    expose_as: 'Documentation preview'
-    paths:
-    - public/
   rules:
     - if: *is-pre-merge
       changes: *docs-or-ci