Don't use private class WrapHandle

The WrapHandle class:

o Isn't actual part of the signature of these methods
o Is a private class (internal to the methods on Routine), so we can't
  refer to it at this level and expect the signatures to compile.

also fix a typo.

Closes #1254

Author: coke

doc/Type/Routine.pod6

@@ -90,22 +90,24 @@ methods, the first element of the Capture needs to be the invocant:
 
 =head2 method wrap
 
-    method wrap(Routine:D: &wrapper --> WrapHandle:D)
+    method wrap(Routine:D: &wrapper)
 
 Wraps (i.e. in-place modifies) the routine. That means a call to this routine
 first calls C<&wrapper>, which then can (but doesn't have to) call the
 original routine with the C<callsame>, C<callwith>, C<nextsame> and
 C<nextwith> dispatchers. The return value from the routine is also
 the return value from the wrapper.
 
-C<wrap> returns a L<WrapHandle|/type/WrapHandle>, which you can pass to L<unwrap> to restore
-the original routine.
+C<wrap> returns an instance of a private class called L<WrapHandle|/type/WrapHandle>,
+which you can pass to L<unwrap> to restore the original routine.
 
 =head2 method unwrap
 
-    method unwrap(Routine:D: WrapHandle $wraphandle)
+    method unwrap($wraphandle)
 
-Restores the original routine after it has been wrapped with L<wrap>.
+Restores the original routine after it has been wrapped with L<wrap>. While
+the signature allows any type to be passed, only the L<WrapHandle|/type/WrapHandle>
+type returned from C<wrap> can usefully be.
 
 =head2 method yada
 

doc/Type/WrapHandle.pod6

@@ -6,7 +6,7 @@
 
 class WrapHandle { ... }
 
-C<WrapHandle> is created and returned by L<wrap|/type/Routine#method_wrap>. It's only use is to unwrap wrapped routines. Either call L<unwrap|/type/Routine#method_unwrap> on a routine object or call the method C<restore> on a C<WrapHandle> object.
+C<WrapHandle> is created and returned by L<wrap|/type/Routine#method_wrap>. Its only use is to unwrap wrapped routines. Either call L<unwrap|/type/Routine#method_unwrap> on a routine object or call the method C<restore> on a C<WrapHandle> object.
 
     sub f() { say 'f was called' }
     my $wrap-handle = &f.wrap({ say 'before'; callsame; say 'after' });