[CHORE] Remove Microsoft SQL Server Support

- Per https://codeberg.org/forgejo/discussions/issues/122

models/db/convert.go

@@ -47,33 +47,6 @@ func ConvertDatabaseTable() error {
 	return nil
 }
 
-// ConvertVarcharToNVarchar converts database and tables from varchar to nvarchar if it's mssql
-func ConvertVarcharToNVarchar() error {
-	if x.Dialect().URI().DBType != schemas.MSSQL {
-		return nil
-	}
-
-	sess := x.NewSession()
-	defer sess.Close()
-	res, err := sess.QuerySliceString(`SELECT 'ALTER TABLE ' + OBJECT_NAME(SC.object_id) + ' MODIFY SC.name NVARCHAR(' + CONVERT(VARCHAR(5),SC.max_length) + ')'
-FROM SYS.columns SC
-JOIN SYS.types ST
-ON SC.system_type_id = ST.system_type_id
-AND SC.user_type_id = ST.user_type_id
-WHERE ST.name ='varchar'`)
-	if err != nil {
-		return err
-	}
-	for _, row := range res {
-		if len(row) == 1 {
-			if _, err = sess.Exec(row[0]); err != nil {
-				return err
-			}
-		}
-	}
-	return err
-}
-
 // Cell2Int64 converts a xorm.Cell type to int64,
 // and handles possible irregular cases.
 func Cell2Int64(val xorm.Cell) int64 {