Fix nondeterminism error in schema creation.

microrm/src/schema/build.rs

@@ -172,7 +172,7 @@ pub(crate) fn collect_from_database<DB: Database>() -> DatabaseSchema {
 
                     assoc_table
                         .constraints
-                        .push(format!("UNIQUE(`range`, `domain`)"));
+                        .push(format!("unique(`range`, `domain`)"));
 
                     tables.insert(assoc_table_name.clone(), assoc_table);
                 }