Fixed typo

Author: Jan-Olof Hendig

doc/Type/CallFrame.pod6

@@ -54,7 +54,7 @@ This is a shortcut for looking up the C<file> annotation. Therefore, the followi
     my $frame = callframe(0);
     say $frame.file eq $frame.annotations<file>;
 
-head2 method level
+=head2 method level
 
     method level(CallFrame:D:)