Enable stable channel in CI scripts

This was previously disabled to wait for 1.47.0 which contains the
renaming of "intra_doc_link_resoultion_failure" to
"broken_intradoc_link".

.github/workflows/ci.yml

@@ -24,7 +24,7 @@ jobs:
     strategy:
       matrix:
         rust:
-          # - stable   # add again on oct 8th
+          - stable
           - beta
           - nightly
     steps: