chore: remove redundant MTC volumes from pathways template

MTC volumes are dynamically generated by storage.go and injected into VolumeMountsYAML and VolumesYAML for both pathways and non-pathways jobs. The sidecar initContainer still uses hardcoded mounts as it intentionally bypasses the global VolumeMountsYAML block.

Author: Neelabh94

pathways_jobset.tmpl.orig

@@ -536,7 +536,8 @@ func TestGeneratePathwaysManifest_MTC(t *testing.T) {
 			GCSLocation:                 "gs://my-bucket",
 			HeadNodePool:                "pathways-np",
 		},
-		MTCEnabled: true,
+		IsPathwaysJob: true,
+		MTCEnabled:    true,
 	}
 
 	mockResponses := map[string][]shell.CommandResult{