updating ldms github url

Author: spwalto

.github/workflows/darshan_ldms_test_ci.yml

@@ -35,7 +35,7 @@ jobs:
       with:
         repository: ovis-hpc/ldms
         path: ldms
-        ref: OVIS-4
+        ref: main
     - name: Install LDMS
       run: |
         cd ldms