Fix rgbasm(1) formatting

Author: Rangi42

man/rgbasm.1

@@ -200,7 +200,7 @@ section for a list of warnings.
 Disable all warning output, even when turned into errors.
 .It Fl X Ar max_errors , Fl \-max-errors Ar max_errors
 If more than this number of errors (not warnings) occur, then abort the assembly process;
-.Fl X 0
+.Fl X Ar 0
 disables this behavior.
 The default is 100 if
 .Nm