xso-proc: remove stripping of trailing _ from type names

Users can now rename the generated types altogether, which means that we
do not need this anymore to avoid lints.

xso/ChangeLog

@@ -1,12 +1,5 @@
 Version NEXT:
 0000-00-00 Jonas Schäfer <jonas@zombofant.net>
-    * Breaking
-      - We now strip trailing underscores from identifiers before constructing
-        any type names we declare from derive macros.
-
-        If you previously derived any of the macros on e.g. `Foo` and `Foo_`
-        within the same scope, you can use the newly added `builder` and
-        `iterator` meta keys to override the generated type names.
     * Added
       - Support for child elements in derive macros. Child elements may also
         be wrapped in Option or Box.

xso/src/from_xml_doc.md

@@ -69,8 +69,7 @@ identifiers passed to either of these keys is considered reserved.
 
 By default, the builder type uses the type's name suffixed with
 `FromXmlBuilder` and the iterator type uses the type's name suffixed with
-`AsXmlIterator`. If the target type has any trailing underscores, they are
-removed before making the type name.
+`AsXmlIterator`.
 
 ### Field meta