add missing imports

Author: rnro

Sources/GRPCInteropTests/InteroperabilityTestCases.swift

@@ -15,6 +15,7 @@
  */
 
 internal import GRPCCore
+import SwiftProtobuf
 
 private import struct Foundation.Data
 

Sources/GRPCInteropTests/TestService.swift

@@ -16,6 +16,7 @@
 
 private import Foundation
 public import GRPCCore
+import SwiftProtobuf
 
 public struct TestService: Grpc_Testing_TestService.ServiceProtocol {
   public init() {}

Tests/GRPCHealthServiceTests/HealthTests.swift

@@ -17,6 +17,7 @@
 import GRPCCore
 import GRPCHealthService
 import GRPCInProcessTransport
+import SwiftProtobuf
 import XCTest
 
 final class HealthTests: XCTestCase {