Fix typo in readme

Author: 5k4nd

README.md

@@ -32,7 +32,7 @@ Upgrade the plugin
 In order to upgrade the plugin, one can simply run for example `./prepare-version.sh 7.17.28`. It will:
 - fetch dependencies versions form Elasticsearch internals
 - upgrade the right configuration files
-- build the .jar package inside /build/distributions/ using gradle
+- build the .zip module inside /build/distributions/ using gradle