README.md: Correct gradle protobuf reference from 3.22.3 to 3.24.0 (#10772)

1. The bump to `3.23.4` was incorrectly done to the master README in
   #10359.
2. This was reverted in #10430.
3. Then protobuf was upgraded again in 1.58.0, from `3.23.4` to
   `3.24.0` (f8baa9c)
4. 1.58.0 release updated it to `3.24.0` for maven, but kept at
  `3.22.3` for gradle (75af7ab).

Author: sergiitk

README.md

@@ -157,7 +157,7 @@ plugins {
 
 protobuf {
   protoc {
-    artifact = "com.google.protobuf:protoc:3.22.3"
+    artifact = "com.google.protobuf:protoc:3.24.0"
   }
   plugins {
     grpc {
@@ -190,7 +190,7 @@ plugins {
 
 protobuf {
   protoc {
-    artifact = "com.google.protobuf:protoc:3.22.3"
+    artifact = "com.google.protobuf:protoc:3.24.0"
   }
   plugins {
     grpc {