docs: Fix default value for CI_ONIRO_MANIFEST_MIRROR

This reflects the CI reality in the docs.

Signed-off-by: Andrei Gherzan <andrei.gherzan@huawei.com>

docs/ci/hidden-jobs/workspace.rst

@@ -88,7 +88,7 @@ Name of the ``git-repo`` mirror matching to use, expressed as a directory name
 in the shared disk volume. Check the section about git-repo mirror below, for
 details.
 
-The default value is ``ostc-develop``.
+The default value is ``oniro-develop``.
 
 CI_ONIRO_GIT_REPO_PATH
 ----------------------