CppEditor: Remove invalid QTC_ASSERTs in signature synchronizer

They were triggered for

    void f(void);
    void f() {} // add space in parameter list to trigger

Change-Id: I410f3ac13380429a1803b95576afa92fef1fe4cf
Reviewed-by: Fawzi Mohamed <fawzi.mohamed@theqtcompany.com>
Subversion: Remove some dead code

Change-Id: I6f94ecdfb003eac9cc1eaf4460bb4d4a07e883f1
Reviewed-by: Orgad Shaneh <orgads@gmail.com>