Collapse the INVALID_ARGUMENTS error rows and clarify

For ControllerModifyVolume, clarify that INVALID_ARGUMENT is an
infeasible error and that the SP has not made any changes, so
the CO does not need to retry.

Author: bswartz

spec.md

@@ -1711,8 +1711,7 @@ message ControllerModifyVolumeResponse {
 
 | Condition | gRPC Code | Description | Recovery Behavior |
 |-----------|-----------|-------------|-------------------|
-| Parameters not supported | 3 INVALID_ARGUMENT | Indicates that the CO has specified mutable parameters not supported by the volume. | Caller MAY verify mutable parameters. |
-| Exceeds capabilities | 3 INVALID_ARGUMENT | Indicates that the CO has specified capabilities not supported by the volume. | Caller MAY verify volume capabilities by calling ValidateVolumeCapabilities and retry with matching capabilities. |
+| Parameters not supported | 3 INVALID_ARGUMENT | Indicates that the CO has specified invalid mutable parameter keys or values, or the specified volume cannot support the specified parameters. | Caller MAY verify volume capabilities by calling ValidateVolumeCapabilities and retry with matching capabilities. Indicates that no changes were made by the SP. |
 | Volume does not exist | 5 NOT_FOUND | Indicates that a volume corresponding to the specified volume_id does not exist. | Caller MUST verify that the volume_id is correct and that the volume is accessible and has not been deleted before retrying with exponential back off. |
 
 #### `GetCapacity`