MINOR: Remove Kafka release section from root README (apache#19483)

Addressed the feedback
apache#19420 (comment)

Reviewers: TengYao Chi <[email protected]>, PoAn Yang
<[email protected]>, Chia-Ping Tsai <[email protected]>

Author: johnny94

README.md

@@ -277,14 +277,6 @@ See [trogdor/README.md](trogdor/README.md).
 
 See [vagrant/README.md](vagrant/README.md).
 
-### Release Kafka ###
-
-See [release/README.md](release/README.md).
-
-### Official Documentation ###
-
-See [docs/README.md](docs/README.md).
-
 ### Kafka client examples ###
 
 See [examples/README.md](examples/README.md).