Cleanup from removed column and overlooked CONCAT

Forgot to clean comma from removed column and the very CONCAT used as an example in mtxr#440, was not converted using the ISNULL() approach.

packages/core/dialect/mssql/queries.ts

@@ -98,10 +98,10 @@ SELECT
   f.specific_name AS name,
   f.routine_schema AS dbSchema,
   f.routine_catalog AS dbName,
-  concat(
-    f.routine_schema,
-    '.',
-    f.routine_name    
+  (
+    ISNULL(f.routine_schema, '') +
+    ISNULL('.', '') +
+    ISNULL(f.routine_name, '')
   ) as signature,
   COALESCE(STUFF
   (
@@ -123,7 +123,7 @@ SELECT
     ) +
     ISNULL('${TREE_SEP}', '') +
     ISNULL(f.specific_name, '')
-  ) AS tree,
+  ) AS tree
 FROM
   information_schema.routines AS f
   LEFT JOIN information_schema.parameters AS p ON (