tests: fix -Wdeprecated warning

With recent compilers:

    input.yy:49:5: error: definition of implicit copy assignment
                          operator for 'Object' is deprecated because
                          it has a user-declared destructor
                          [-Werror,-Wdeprecated]
        ~Object ()
        ^
    input.yy:130:35: note: in implicit copy assignment operator for
                           'Object' first required here
        { yylhs.value.as< Object > () = yystack_[0].value.as< Object > (); }

* tests/c++.at (Object): Add missing assignment operator.

0 files changed, 0 insertions, 0 deletions