Comment out ambiguous mangled name

Currently this test relies on the system-installed c++filt.
The newer binutils (2.36.1) has a fix which changes one of the
symbols' demanglings. For now, just disable the troublesome line.

New binutils:
```
$ c++filt _ZSt8__equal4IPKcS1_ZNSt8__detail16_Backref_matcherIS1_NSt7__cxx1112regex_traitsIcEEE8_M_applyES1_S1_S1_S1_EUlccE_EbT_S9_T0_SA_T1_
bool std::__equal4<char const*, char const*, std::__detail::_Backref_matcher<char const*, std::__cxx11::regex_traits<char> >::_M_apply(char const*, char const*, char const*, char const*)::{lambda(char, char)#1}>(char const*, char const*, char const*, char const*, std::__detail::_Backref_matcher<char const*, std::__cxx11::regex_traits<char> >::_M_apply(char const*, char const*, char const*, char const*)::{lambda(char, char)#1})
```

Old binutils:
```
$ c++filt _ZSt8__equal4IPKcS1_ZNSt8__detail16_Backref_matcherIS1_NSt7__cxx1112regex_traitsIcEEE8_M_applyES1_S1_S1_S1_EUlccE_EbT_S9_T0_SA_T1_
bool std::__equal4<char const*, char const*, std::__detail::_Backref_matcher<char const*, std::__cxx11::regex_traits<char> >::_M_apply(char const*, char const*, char const*, char const*)::{lambda(char, char)#1}>(char const*, std::__detail::_Backref_matcher<char const*, std::__cxx11::regex_traits<char> >::_M_apply(char const*, char const*, char const*, char const*)::{lambda(char, char)#1}, char const*, char const*, std::__detail::_Backref_matcher<char const*, std::__cxx11::regex_traits<char> >::_M_apply(char const*, char const*, char const*, char const*)::{lambda(char, char)#1})
```