Fix zone specification in HdT tests

Author: sunnylovestiramisu

test/e2e/tests/single_zone_e2e_test.go

@@ -276,10 +276,6 @@ var _ = Describe("GCE PD CSI Driver", func() {
 			client := testContext.Client
 			instance := testContext.Instance
 
-			if diskType == hdtDiskType {
-				z = "us-east4-a"
-			}
-
 			volName, _ := createAndValidateUniqueZonalDisk(client, p, z, diskType)
 
 			underSpecifiedID := common.GenerateUnderspecifiedVolumeID(volName, true /* isZonal */)