test: tentatively disable SELinux tests

Currently, mkosi GitHub action complains the following:
===
Could not find 'setfiles' which is required to relabel files.
===
Let's tentatively disable SELinux test.

.github/workflows/mkosi.yml

@@ -80,14 +80,14 @@ jobs:
             sanitizers: ""
             llvm: 0
             cflags: "-Og"
-            relabel: yes
+            relabel: no
             qemu: 0
           - distro: fedora
             release: rawhide
             sanitizers: address,undefined
             llvm: 1
             cflags: "-Og"
-            relabel: yes
+            relabel: no
             qemu: 0
           - distro: opensuse
             release: tumbleweed
@@ -101,14 +101,14 @@ jobs:
             sanitizers: ""
             llvm: 0
             cflags: "-Og"
-            relabel: yes
+            relabel: no
             qemu: 0
           - distro: centos
             release: "10"
             sanitizers: ""
             llvm: 0
             cflags: "-Og"
-            relabel: yes
+            relabel: no
             qemu: 0
 
     steps:

test/meson.build

@@ -320,7 +320,6 @@ foreach dirname : [
         'TEST-03-JOBS',
         'TEST-04-JOURNAL',
         'TEST-05-RLIMITS',
-        'TEST-06-SELINUX',
         'TEST-07-PID1',
         'TEST-08-INITRD',
         'TEST-09-REBOOT',