travis: Temporarily remove openSUSE Tumbleweed

Tumbleweed uses glibc 2.33, which introduced incompatibility
(uses faccessat2) [1], which requires libseccomp v2.5.0.
The newest Ubuntu in Travis (actually any Ubuntu) has 2.4.3,
thus temporarily remove openSUSE Tumbleweed.

[1] seccomp/libseccomp#314

Signed-off-by: Petr Vorel <pvorel@suse.cz>

.travis.yml

@@ -55,10 +55,6 @@ matrix:
           env: DISTRO=debian:oldstable
           compiler: clang
 
-        - os: linux
-          env: DISTRO=opensuse/tumbleweed
-          compiler: gcc
-
         - os: linux
           env: DISTRO=opensuse/leap
           compiler: gcc