Bump to HAProxy 2.6.13

Bump the HAProxy version in dist-git so that OCP 4.13 ships HAProxy 2.6.13, with this patch added on top: https://git.haproxy.org/?p=haproxy-2.6.git;a=commit;h=2b0aafdc92f691bc4b987300c9001a7cc3fb8d08. The patch fixes the segfault that was being tracked as OCPBUGS-13232.

This patch is in HAProxy 2.6.14, so we can stop carrying the patch once we bump to HAProxy 2.6.14 or newer in a subsequent OCP release.