remove manifest

Author: avik-pal

.github/workflows/Downstream.yml

@@ -55,6 +55,9 @@ jobs:
             @info "Not compatible with this release. No problem." exception=err
             exit(0)  # Exit immediately, as a success
           end
+        env:
+          RETESTITEMS_NWORKERS: 4
+          RETESTITEMS_NWORKER_THREADS: 2
       - uses: julia-actions/julia-processcoverage@v1
         with:
           directories: src,ext