ESQL: Fix grammar changes around per agg filtering (#114848)

Remove dev flag left in grammar for agg filtering
Related to #113735

Author: costin

docs/changelog/114848.yaml

@@ -0,0 +1,5 @@
+pr: 114848
+summary: "ESQL: Fix grammar changes around per agg filtering"
+area: ES|QL
+type: bug
+issues: []

x-pack/plugin/esql/src/main/antlr/EsqlBaseLexer.g4

@@ -209,7 +209,7 @@ SLASH : '/';
 PERCENT : '%';
 
 MATCH : 'match';
-NESTED_WHERE : {this.isDevVersion()}? WHERE -> type(WHERE);
+NESTED_WHERE : WHERE -> type(WHERE);
 
 NAMED_OR_POSITIONAL_PARAM
     : PARAM (LETTER | UNDERSCORE) UNQUOTED_ID_BODY*

x-pack/plugin/esql/src/main/antlr/EsqlBaseParser.g4

@@ -173,7 +173,7 @@ aggFields
     ;
 
 aggField
-    : field {this.isDevVersion()}? (WHERE booleanExpression)?
+    : field (WHERE booleanExpression)?
     ;
 
 qualifiedName