Fix location of sql cli jar

The `elasticsearch` directory in the plugin folder structure was
removed, so make sure the CLI jar ends up in $ES_HOME/bin/x-pack as
intended

Follow up from elastic/x-pack-elasticsearch#28589

Original commit: elastic/x-pack-elasticsearch@6580b38fe0

plugin/sql/build.gradle

@@ -35,12 +35,13 @@ dependencies {
     }
 }
 
-/* Bundle the sql-cli into the binary files. This is useful
- * because it is an executable jar that can be moved wherever
- * it is needed. */
+/* Bundle the sql-cli into the binary files. It should end up
+ * in $ES_HOME/bin/x-pack/. This is useful because it is an
+ * executable jar that can be moved wherever it is needed.
+ */
 bundlePlugin {
     from (configurations.bin) {
-        into 'elasticsearch/bin'
+        into 'bin'
     }
 }