Fix synced flush docs
They had some copy and paste errors that failed the docs build.
-[[java-rest-high-flush]]
+[[java-rest-high-flush-synced]]
=== Flush Synced API
[[java-rest-high-flush-synced-request]]
@@ -60,7 +60,7 @@ include-tagged::{doc-tests}/IndicesClientDocumentationIT.java[flush-synced-execu
provided as an argument
<2> Called in case of failure. The raised exception is provided as an argument
-[[java-rest-high-flush-response]]
+[[java-rest-high-flush-synced-response]]
==== Flush Synced Response
The returned `SyncedFlushResponse` allows to retrieve information about the
