Remove ReturnMatcher alias

As pointed out by @tlambert03, we can just use the single TypeMatcher
alias

magicgui/type_map.py

@@ -27,7 +27,6 @@
 from magicgui.types import (
     PathLike,
     ReturnCallback,
-    ReturnMatcher,
     TypeMatcher,
     WidgetClass,
     WidgetOptions,
@@ -44,7 +43,7 @@ class MissingWidget(RuntimeError):
 
 
 _RETURN_CALLBACKS: DefaultDict[type, list[ReturnCallback]] = defaultdict(list)
-_RETURN_MATCHERS: list[ReturnMatcher] = list()
+_RETURN_MATCHERS: list[TypeMatcher] = list()
 _TYPE_MATCHERS: list[TypeMatcher] = list()
 _TYPE_DEFS: dict[type, WidgetTuple] = dict()
 
@@ -114,12 +113,12 @@ def type_matcher(func: TypeMatcher) -> TypeMatcher:
     return func
 
 
-def return_matcher(func: ReturnMatcher) -> ReturnMatcher:
+def return_matcher(func: TypeMatcher) -> TypeMatcher:
     """Add function to the set of return matchers.
 
     Example
     -------
-    >>> @return
+    >>> @return_matcher
     ... def default_return_widget(value, annotation):
     ...     return widgets.LineEdit, {}
     """