disable ReplaceStringCasingWithInsensitiveRegexMatch rule in 8.19

Author: julian-elastic

x-pack/plugin/esql/qa/testFixtures/src/main/resources/where-like.csv-spec

@@ -874,3 +874,15 @@ emp_no:integer |first_name:keyword
 10001          |Georgi
 10055          |Georgy
 ;
+
+rlikeWithLowerTurnedInsensitiveUnicode#[skip:-8.12.99]
+FROM airport_city_boundaries
+| WHERE TO_UPPER(region) RLIKE ".*Л.*" and abbrev == "FRU"
+| KEEP region
+;
+
+region:text
+Свердлов району
+;
+
+

x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/optimizer/LocalLogicalPlanOptimizer.java

@@ -9,7 +9,6 @@
 
 import org.elasticsearch.xpack.esql.optimizer.rules.logical.PropagateEmptyRelation;
 import org.elasticsearch.xpack.esql.optimizer.rules.logical.ReplaceStatsFilteredAggWithEval;
-import org.elasticsearch.xpack.esql.optimizer.rules.logical.ReplaceStringCasingWithInsensitiveRegexMatch;
 import org.elasticsearch.xpack.esql.optimizer.rules.logical.local.InferIsNotNull;
 import org.elasticsearch.xpack.esql.optimizer.rules.logical.local.InferNonNullAggConstraint;
 import org.elasticsearch.xpack.esql.optimizer.rules.logical.local.LocalPropagateEmptyRelation;
@@ -75,7 +74,9 @@ private static Batch<LogicalPlan> localOperators() {
         }
 
         // add rule that should only apply locally
-        newRules.add(new ReplaceStringCasingWithInsensitiveRegexMatch());
+        // Disabled until Unicode CASE_INSENSITIVE support is added to Lucine 9.0
+        // waiting on https://github.com/elastic/elasticsearch/issues/131386
+        // newRules.add(new ReplaceStringCasingWithInsensitiveRegexMatch());
 
         return operators.with(newRules.toArray(Rule[]::new));
     }