ESQL: Run LOOKUP docs test only in SNAPSHOT (#109493)

LOOKUP is only registered on SNAPSHOT builds.

closes #109478

docs/build.gradle

@@ -36,6 +36,15 @@ ext.docsFileTree = fileTree(projectDir) {
   }
 }
 
+tasks.named("yamlRestTest") {
+  if (BuildParams.isSnapshotBuild() == false) {
+    // LOOKUP is not available in snapshots
+    systemProperty 'tests.rest.blacklist', [
+      "reference/esql/processing-commands/lookup/esql-lookup-example"
+    ].join(',')
+  }
+}
+
 /* List of files that have snippets that will not work until platinum tests can occur ... */
 tasks.named("buildRestTests").configure {
   getExpectedUnconvertedCandidates().addAll(

docs/reference/esql/processing-commands/lookup.asciidoc

@@ -27,7 +27,7 @@ adding the other fields from the `table` to the output.
 *Examples*
 
 // tag::examples[]
-[source,console]
+[source,console,id=esql-lookup-example]
 ----
 POST /_query?format=txt
 {

muted-tests.yml

@@ -59,9 +59,6 @@ tests:
 - class: org.elasticsearch.xpack.esql.expression.function.scalar.multivalue.MvAppendTests
   method: testEvaluateBlockWithoutNulls {TestCase=<cartesian_shape>, <cartesian_shape>}
   issue: https://github.com/elastic/elasticsearch/issues/109409
-- class: "org.elasticsearch.smoketest.DocsClientYamlTestSuiteIT"
-  issue: "https://github.com/elastic/elasticsearch/issues/109478"
-  method: "test {yaml=reference/esql/processing-commands/lookup/line_31}"
 - class: DenseVectorMappingUpdateIT
   issue: "https://github.com/elastic/elasticsearch/issues/109571"
 - class: "org.elasticsearch.compute.lucene.TimeSeriesSortedSourceOperatorTests"