Fixes DesiredBalanceComputerTests Failure (#135183)

Increases the threshold for convergence inside the
DesiredBalanceComputerTests
.testDesiredBalanceShouldConvergeInABigCluster from 1000 to 2000.
Some randomly generated clusters have large numbers of shards, and the previous 1000
threshold was too restrictive. The test is also unmuted.

Closes: 135123

Author: joshua-adams-1

muted-tests.yml

@@ -591,9 +591,6 @@ tests:
 - class: org.elasticsearch.xpack.esql.heap_attack.HeapAttackIT
   method: testLookupExplosionBigString
   issue: https://github.com/elastic/elasticsearch/issues/135122
-- class: org.elasticsearch.cluster.routing.allocation.allocator.DesiredBalanceComputerTests
-  method: testDesiredBalanceShouldConvergeInABigCluster
-  issue: https://github.com/elastic/elasticsearch/issues/135123
 - class: org.elasticsearch.xpack.test.rest.XPackRestIT
   method: test {p0=transform/transforms_start_stop/Test stop transform with force and wait_for_checkpoint true}
   issue: https://github.com/elastic/elasticsearch/issues/135135

server/src/test/java/org/elasticsearch/cluster/routing/allocation/allocator/DesiredBalanceComputerTests.java

@@ -717,7 +717,7 @@ public void testDesiredBalanceShouldConvergeInABigCluster() {
             DesiredBalance.BECOME_MASTER_INITIAL,
             input,
             queue(),
-            ignored -> iteration.incrementAndGet() < 1000
+            ignored -> iteration.incrementAndGet() < 2000
         );
 
         var desiredDiskUsage = Maps.<String, Long>newMapWithExpectedSize(nodes);