Fix formatting typo in man/rgbasm-old.5

Author: Rangi42

man/rgbasm-old.5

@@ -370,7 +370,7 @@ or
 Deprecated in 1.0.0.
 .Pp
 Instead, use
-.Dl -Wno-overwrite .
+.Ql -Wno-overwrite .
 .Ss rgbgfx -h/--horizontal
 Removed in 0.6.0.
 .Pp