[gitian] Don't call "make check-symbols"

Currently it does not recognise any of the C++11 symbols. We can re-enable this
when either we update it, or upstream migrates to C++11 and does so.

contrib/gitian-descriptors/gitian-linux.yml

@@ -110,7 +110,6 @@ script: |
     CONFIG_SITE=${BASEPREFIX}/${i}/share/config.site ./configure --prefix=/ --disable-ccache --disable-maintainer-mode --disable-dependency-tracking ${CONFIGFLAGS} CFLAGS="${HOST_CFLAGS}" CXXFLAGS="${HOST_CXXFLAGS}" LDFLAGS="${HOST_LDFLAGS}"
     make ${MAKEOPTS}
     make ${MAKEOPTS} -C src check-security
-    make ${MAKEOPTS} -C src check-symbols
     make install DESTDIR=${INSTALLPATH}
     cd installed
     find . -name "lib*.la" -delete