HBASE-29701 Update README.txt in hbase-protocol-shaded (#7443)

Signed-off-by: Duo Zhang <[email protected]>
Signed-off-by: Nihal Jain <[email protected]>
(cherry picked from commit d41d5c1)

Author: stoty

hbase-protocol-shaded/README.txt

@@ -1,9 +1,9 @@
-This module has proto files used by core. These protos
-overlap with protos that are used by coprocessor endpoints
-(CPEP) in the module hbase-protocol. So core versions have
-a different name, the generated classes are relocated
--- i.e. shaded -- to a new location; they are moved from
-org.apache.hadoop.hbase.* to org.apache.hadoop.hbase.shaded.
+This module has proto files used by core.
+For historical reasons and to signify that the generated classes are using
+the relocated hbase-thirdparty protobuf-java library the generated classes are in
+the org.apache.hadoop.hbase.shaded.protobuf.generated.* package, instead of the old
+org.apache.hadoop.hbase.protobuf.generated.* package, which is not used at all by
+Hbase 3 and later versions.
 
 proto files layout:
 protobuf/client - client to server messages, client rpc service and protos, used in hbase-client exclusively;