Do not do the EXISTS-to-IN transformation if the sub-select has LIMIT clause.

FossilOrigin-Name: d07e246f9b6d4d7aef63a6debcb7ab2832bff6f80a245f50bcebb3f8de1bacc7

test/exists2.test

@@ -164,6 +164,12 @@ do_execsql_test 2.7a {
   four one
 }
 
+do_execsql_test 2.7b {
+  SELECT a FROM t3 WHERE EXISTS (SELECT 1 FROM t4 WHERE (a,x)=(c,y) LIMIT 1)
+} {
+  four one
+}
+
 # EXISTS clauses using vector expressions in the WHERE clause.
 #
 reset_db