Drop the Hurd socket patch that it is already applied upstream

The author Samuel Thibault confirmed the patch can be dropped due
to the issue being fixed by upstream by now.

debian/patches/hurd_socket.patch

-From: Debian MySQL Maintainers <pkg-mysql-maint@lists.alioth.debian.org>
-Date: Thu, 10 Aug 2017 20:40:29 +0200
-Subject: hurd_socket
-
----
- mysql-test/lib/My/Platform.pm | 2 ++
- 1 file changed, 2 insertions(+)
-
---- a/mysql-test/lib/My/Platform.pm
-+++ b/mysql-test/lib/My/Platform.pm
-@@ -112,6 +112,8 @@ sub check_socket_path_length {
-   return 0 if ($^O eq 'aix');
-   # See Debian bug #670722 - failing on kFreeBSD even after setting short path
-   return 0 if $^O eq 'gnukfreebsd' and length $path < 40;
-+  # GNU/Hurd doesn't have hostpath(), but no limitation either.
-+  return 0 if $^O eq 'gnu';
- 
-   require IO::Socket::UNIX;
- 

debian/patches/series

@@ -6,7 +6,6 @@ innodb_simulate_comp_test_speedup.patch
 mips-groonga-atomic.patch
 mips-connect-unaligned.patch
 mips-machine.patch
-#hurd_socket.patch
 #armhf_mroonga_storage_fail.patch
 #c11_atomics.patch
 kFreeBSD-gettid.patch
@@ -18,4 +17,3 @@ Add_default_ExecStartPre_to_mariadb@.service.patch
 hurd.patch
 mips-compilation-failure-__bss_start-symbol-miss.patch
 stronger-openssl-1.1.0-compatible-keys.patch
-