Remove Xvfb dependency

A quick look through ibus' `test-glib-simple-items` source code doesn't
point to it actually needing an X11 server. So let's remove Xvfb since
we're trying to get rid of it.

libdbusmenu.spec

@@ -52,9 +52,6 @@ BuildRequires:  pkgconfig(gtk+-3.0) >= 2.91
 BuildRequires:  pkgconfig(json-glib-1.0) >= 0.13.4
 BuildRequires:  pkgconfig(x11) >= 1.3
 BuildRequires:  vala
-%if 0%{?rhel} > 9
-BuildRequires:  xorg-x11-server-Xvfb
-%endif
 
 # pkgconfig file is checked for valgrind, but is actually only used for tests
 # https://bugzilla.redhat.com/show_bug.cgi?id=1262274

tests/test-glib-simple-items/main.fmf

@@ -4,4 +4,3 @@ framework: beakerlib
 require:
     - git
     - libdbusmenu-gtk3-tests
-    - xorg-x11-server-Xvfb

tests/test-glib-simple-items/test.sh

@@ -6,20 +6,13 @@ rlJournalStart
     rlPhaseStartSetup
         rlRun "tmp=\$(mktemp -d)" 0 "Create tmp directory"
         rlRun "pushd $tmp"
-        rlRun "export DISPLAY=:99.0"
-        rlRun "/usr/bin/Xvfb $DISPLAY -noreset +extension GLX +extension RANDR +extension RENDER -screen 0 1280x1024x24 &"
-        rlRun "echo $! > X_PID"
-        rlRun "sleep 5"
-        rlRun "set -o pipefail"
     rlPhaseEnd
 
     rlPhaseStartTest
-        rlRun "export DISPLAY=:99.0"
-        rlRun "/usr/libexec/libdbusmenu-gtk3/test-glib-simple-items >output 2>&1" 0
+        rlRun "/usr/libexec/libdbusmenu-gtk3/test-glib-simple-items >output 2>&1"
     rlPhaseEnd
 
     rlPhaseStartCleanup
-        rlRun "kill -9 $(cat X_PID)"
         rlRun "popd"
         rlRun "rm -r $tmp" 0 "Remove tmp directory"
     rlPhaseEnd