fix(ci): point to shared-workflows branch that enables overriding cpp artifact name

Author: gforsyth

.github/workflows/pr.yaml

@@ -195,7 +195,7 @@ jobs:
   conda-cpp-build:
     needs: checks
     secrets: inherit
-    uses: rapidsai/shared-workflows/.github/workflows/conda-cpp-build.yaml@main
+    uses: rapidsai/shared-workflows/.github/workflows/conda-cpp-build.yaml@cpp_override
     with:
       build_type: pull-request
       node_type: cpu8