ES|QL: unmute generative tests (elastic#138232)

Fixes: elastic#137909

Unmuting Generative tests and adding an exception for `Plan ...
optimized incorrectly due to missing references`

Author: luigidellaquila

muted-tests.yml

@@ -423,9 +423,6 @@ tests:
 - class: org.elasticsearch.xpack.inference.integration.AuthorizationTaskExecutorMultipleNodesIT
   method: testAuthorizationTaskGetsRelocatedToAnotherNode_WhenTheNodeThatIsRunningItShutsDown
   issue: https://github.com/elastic/elasticsearch/issues/137911
-- class: org.elasticsearch.xpack.esql.qa.multi_node.GenerativeIT
-  method: test
-  issue: https://github.com/elastic/elasticsearch/issues/137909
 - class: org.elasticsearch.xpack.inference.integration.AuthorizationTaskExecutorIT
   method: testCreatesChatCompletion_AndThenCreatesTextEmbedding
   issue: https://github.com/elastic/elasticsearch/issues/138012
@@ -438,9 +435,6 @@ tests:
 - class: org.elasticsearch.xpack.inference.integration.AuthorizationTaskExecutorMultipleNodesIT
   method: testCancellingAuthorizationTaskRestartsIt
   issue: https://github.com/elastic/elasticsearch/issues/138099
-- class: org.elasticsearch.xpack.esql.qa.single_node.GenerativeIT
-  method: test
-  issue: https://github.com/elastic/elasticsearch/issues/137909
 - class: org.elasticsearch.simdvec.ESVectorUtilTests
   method: testSoarDistanceBulk
   issue: https://github.com/elastic/elasticsearch/issues/138117

x-pack/plugin/esql/qa/server/src/main/java/org/elasticsearch/xpack/esql/qa/rest/generative/GenerativeRestTest.java

@@ -71,6 +71,7 @@ public abstract class GenerativeRestTest extends ESRestTestCase implements Query
         "can't find input for", // https://github.com/elastic/elasticsearch/issues/136596
         "unexpected byte", // https://github.com/elastic/elasticsearch/issues/136598
         "out of bounds for length", // https://github.com/elastic/elasticsearch/issues/136851
+        "optimized incorrectly due to missing references", // https://github.com/elastic/elasticsearch/issues/138231
 
         // Awaiting fixes for correctness
         "Expecting at most \\[.*\\] columns, got \\[.*\\]", // https://github.com/elastic/elasticsearch/issues/129561