[no-release-notes] remove dialect option from merge join tests (#3121)

Author: jycor

enginetest/queries/script_queries.go

@@ -8507,8 +8507,7 @@ where
 	},
 	{
 		// https://github.com/dolthub/dolt/issues/8728
-		Name:    "test merge join optimization (removing sort node over indexed tables) does not break ordering",
-		Dialect: "mysql",
+		Name: "test merge join optimization (removing sort node over indexed tables) does not break ordering",
 		SetUpScript: []string{
 			"create table t1 (i int primary key);",
 			"create table t2 (j int primary key);",