spec: remove topology from validate-volume.

Current thinking is that topology of a volume can be discovered via the
ListVolumes RPC of the controller and is not strictly required here. We
can always add it back later if needed.

Author: James DeFelice

csi.proto

@@ -644,14 +644,10 @@ message ValidateVolumeCapabilitiesRequest {
   // This field is OPTIONAL.
   map<string, string> parameters = 4;
 
-  // See CreateVolumeRequest.accessibility_requirements.
-  // This field is OPTIONAL.
-  TopologyRequirement accessibility_requirements = 5;
-
   // Secrets required by plugin to complete volume validation request.
   // This field is OPTIONAL. Refer to the `Secrets Requirements`
   // section on how to use this field.
-  map<string, string> controller_validate_secrets = 6;
+  map<string, string> controller_validate_secrets = 5;
 }
 
 message ValidateVolumeCapabilitiesResponse {
@@ -664,13 +660,9 @@ message ValidateVolumeCapabilitiesResponse {
     // This field is REQUIRED.
     repeated VolumeCapability volume_capabilities = 2;
 
-    // Topology requirements supported by the plugin.
-    // This field is OPTIONAL.
-    TopologyRequirement accessibility_requirements = 3;
-
     // The volume creation parameters validated by the plugin.
     // This field is OPTIONAL.
-    map<string, string> parameters = 4;
+    map<string, string> parameters = 3;
   }
 
   // Confirmed indicates to the CO the set of capabilities that the