Fix RestoreInProgressAllocationDeciderTests (#135593)

Author: nicktindall

muted-tests.yml

@@ -579,9 +579,6 @@ tests:
 - class: org.elasticsearch.xpack.esql.qa.single_node.EsqlSpecIT
   method: test {csv-spec:spatial_shapes.ConvertCartesianShapeFromStringParseError}
   issue: https://github.com/elastic/elasticsearch/issues/135455
-- class: org.elasticsearch.cluster.routing.allocation.decider.RestoreInProgressAllocationDeciderTests
-  method: testCanAllocatePrimaryExistingInRestoreInProgress
-  issue: https://github.com/elastic/elasticsearch/issues/135566
 - class: org.elasticsearch.xpack.esql.inference.textembedding.TextEmbeddingOperatorTests
   method: testSimpleCircuitBreaking
   issue: https://github.com/elastic/elasticsearch/issues/135569

server/src/test/java/org/elasticsearch/cluster/routing/allocation/decider/RestoreInProgressAllocationDeciderTests.java

@@ -114,7 +114,7 @@ public void testCanAllocatePrimaryExistingInRestoreInProgress() {
             UnassignedInfo.Reason reason;
             if (randomBoolean()) {
                 failureCount = randomBoolean() ? 0 : 1;
-                reason = UnassignedInfo.Reason.ALLOCATION_FAILED;
+                reason = failureCount > 0 ? UnassignedInfo.Reason.ALLOCATION_FAILED : UnassignedInfo.Reason.NEW_INDEX_RESTORED;
             } else {
                 failureCount = 0;
                 reason = currentInfo.reason();