TUN-8052: Update go to 1.21.5

Also update golang.org/x/net and google.golang.org/grpc to fix vulnerabilities,
although cloudflared is using them in a way that is not exposed to those risks

vendor/go.opentelemetry.io/otel/version.go

@@ -16,5 +16,5 @@ package otel // import "go.opentelemetry.io/otel"
 
 // Version is the current release version of OpenTelemetry in use.
 func Version() string {
-	return "1.6.3"
+	return "1.21.0"
 }