Fix gold testsuite failure with GCC 6.
With GCC 6 when not using -static-libstdc++, the operator delete(void*) function is defined in the shared C++ support library, rather than in the main program. The test script is too aggressive in checking for this symbol's presence among the exported symbols. This patch removes the check for that symbol. gold/ PR gold/20310 * testsuite/dynamic_list.sh: Remove check for _ZdlPv.