build(deps): bump google.golang.org/grpc from 1.50.1 to 1.56.3

Bumps [google.golang.org/grpc](https://github.com/grpc/grpc-go) from 1.50.1 to 1.56.3.
- [Release notes](https://github.com/grpc/grpc-go/releases)
- [Commits](https://github.com/grpc/grpc-go/compare/v1.50.1...v1.56.3)

---
updated-dependencies:
- dependency-name: google.golang.org/grpc
  dependency-type: indirect
...

Signed-off-by: dependabot[bot] <support@github.com>

vendor/google.golang.org/grpc/serviceconfig/serviceconfig.go

@@ -0,0 +1,44 @@
+/*
+ *
+ * Copyright 2019 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+// Package serviceconfig defines types and methods for operating on gRPC
+// service configs.
+//
+// # Experimental
+//
+// Notice: This package is EXPERIMENTAL and may be changed or removed in a
+// later release.
+package serviceconfig
+
+// Config represents an opaque data structure holding a service config.
+type Config interface {
+	isServiceConfig()
+}
+
+// LoadBalancingConfig represents an opaque data structure holding a load
+// balancing config.
+type LoadBalancingConfig interface {
+	isLoadBalancingConfig()
+}
+
+// ParseResult contains a service config or an error.  Exactly one must be
+// non-nil.
+type ParseResult struct {
+	Config Config
+	Err    error
+}