formatter: Make inline comments "transparent"

Adding an inline comment somewhere should not affect formatting below
it. So, for inline comments, don't make the line type a comment, but
instead reuse the current line type so that the comment becomes
"transparent".

tests/formatting/correct1.blp

@@ -59,7 +59,7 @@ Adw.MessageDialog {
 }
 
 Adw.Breakpoint {
-  condition ("width < 100")
+  condition ("width < 100") // Another inline comment
 
   setters {
     label2.label: _("Hello, world!");