fix typo

Author: stoned

doc/Language/functions.pod6

@@ -440,7 +440,7 @@ at /tmp/only-redeclaration.p6:3
 ------> <BOL>⏏<EOL>
 =end code
 
-Anonymous sub cannot be declared C<only>. C<only sub {}'> will throw an error of
+Anonymous sub cannot be declared C<only>. C<only sub {}> will throw an error of
 type, surprisingly, C<X::Anon::Multi>.
 
 =head1 Conventions and idioms