Warn users about the grpc-compression-type config (#20935) (#21103)

Author: ti-chi-bot

tikv-configuration-file.md

@@ -140,6 +140,11 @@ This document only describes the parameters that are not included in command-lin
 
 + The compression algorithm for gRPC messages
 + Optional values: `"none"`, `"deflate"`, `"gzip"`
+
+    > **Note:**
+    >
+    > TiDB does not support `"deflate"`. Therefore, if you want to compress gRPC response messages sent from TiKV to TiDB, set this configuration item to `"gzip"`.
+
 + Default value: `"none"`
 
 ### `grpc-concurrency`