Remove usages of obsolete settings

The settings `indices.recovery.concurrent_streams` and
`indices.recovery.concurrent_small_file_streams` were removed in
f5e4cd4. This commit removes their last traces
from the codebase.

Relates elastic#28781

Author: DaveCTurner

server/src/test/java/org/elasticsearch/indices/recovery/RecoverySourceHandlerTests.java

@@ -333,9 +333,7 @@ public void close() throws IOException {
 
 
     public void testHandleExceptinoOnSendSendFiles() throws Throwable {
-        Settings settings = Settings.builder().put("indices.recovery.concurrent_streams", 1).
-            put("indices.recovery.concurrent_small_file_streams", 1).build();
-        final RecoverySettings recoverySettings = new RecoverySettings(settings, service);
+        final RecoverySettings recoverySettings = new RecoverySettings(Settings.EMPTY, service);
         final StartRecoveryRequest request = getStartRecoveryRequest();
         Path tempDir = createTempDir();
         Store store = newStore(tempDir, false);