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/binarylog.go

@@ -32,6 +32,9 @@ var grpclogLogger = grpclog.Component("binarylog")
 
 // Logger specifies MethodLoggers for method names with a Log call that
 // takes a context.
+//
+// This is used in the 1.0 release of gcp/observability, and thus must not be
+// deleted or changed.
 type Logger interface {
 	GetMethodLogger(methodName string) MethodLogger
 }