Explicitly ignore return value of sk_SSL_COMP_delete.

Explicitly cast the returned value into the void. Clang complains
about this unused return value otherwise.

BUG=none
TEST=flip_in_mem_edsm_server

Review URL: http://codereview.chromium.org/5727003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@69111 0039d316-1c4b-4281-b951-d872f2087c98