bump golang.org/grpc to v1.56.3

Bumping golang.org/grpc in light of CVE-2023-44487.

Signed-off-by: Jonathan Gonzalez V <jonathan.abdiel@gmail.com>

vendor/google.golang.org/grpc/internal/binarylog/method_logger.go

@@ -49,6 +49,9 @@ func (g *callIDGenerator) reset() {
 var idGen callIDGenerator
 
 // MethodLogger is the sub-logger for each method.
+//
+// This is used in the 1.0 release of gcp/observability, and thus must not be
+// deleted or changed.
 type MethodLogger interface {
 	Log(context.Context, LogEntryConfig)
 }
@@ -65,6 +68,9 @@ type TruncatingMethodLogger struct {
 }
 
 // NewTruncatingMethodLogger returns a new truncating method logger.
+//
+// This is used in the 1.0 release of gcp/observability, and thus must not be
+// deleted or changed.
 func NewTruncatingMethodLogger(h, m uint64) *TruncatingMethodLogger {
 	return &TruncatingMethodLogger{
 		headerMaxLen:  h,
@@ -145,6 +151,9 @@ func (ml *TruncatingMethodLogger) truncateMessage(msgPb *binlogpb.Message) (trun
 }
 
 // LogEntryConfig represents the configuration for binary log entry.
+//
+// This is used in the 1.0 release of gcp/observability, and thus must not be
+// deleted or changed.
 type LogEntryConfig interface {
 	toProto() *binlogpb.GrpcLogEntry
 }