README.md: fix version typo (#6976)

diff --git a/README.md b/README.md
index 8f1c056..8874151 100644
--- a/README.md
+++ b/README.md
@@ -60,7 +60,7 @@
 ```gradle
 implementation 'io.grpc:grpc-netty-shaded:1.29.0'
 implementation 'io.grpc:grpc-protobuf:1.29.0'
-implementation 'io.grpc:grpc-stub:1.20.0'
+implementation 'io.grpc:grpc-stub:1.29.0'
 ```
 
 For Android client, use `grpc-okhttp` instead of `grpc-netty-shaded` and