[CIR][CI] Remove libcxx tests

Reviewers: bcardosolopes

Reviewed By: bcardosolopes

Pull Request: llvm#881

Author: lanza

.github/workflows/libcxx-build-and-test.yaml

@@ -22,9 +22,6 @@ on:
       - 'runtimes/**'
       - 'cmake/**'
       - '.github/workflows/libcxx-build-and-test.yaml'
-  schedule:
-    # Run nightly at 08:00 UTC (aka 00:00 Pacific, aka 03:00 Eastern)
-    - cron: '0 8 * * *'
 
 permissions:
   contents: read # Default everything to read-only