qemu: conf: fix stray comma

The qemu.conf change broke our augeas test:

qemu/test_libvirtd_qemu.aug:96.3-203.1:exception thrown in test
qemu/test_libvirtd_qemu.aug:96.8-.34:exception: Iterated lens matched less than it should
    Lens: ../../src/qemu/libvirtd_qemu.aug:170.13-.43:
      Last match: ../../src/qemu/libvirtd_qemu.aug:18.52-.113:
      Not matching: ../../src/qemu/libvirtd_qemu.aug:12.19-.31:
    Error encountered at 48:27 (1615 characters into string)
    <\n    "/dev/ptmx", "/dev/kvm"|=|,\n]\nsave_image_format = "raw>

Fixes: ab5ba570Signed-off-by: NJán Tomko <jtomko@redhat.com>

src/qemu/qemu.conf

@@ -494,7 +494,7 @@
 #cgroup_device_acl = [
 #    "/dev/null", "/dev/full", "/dev/zero",
 #    "/dev/random", "/dev/urandom",
-#    "/dev/ptmx", "/dev/kvm",
+#    "/dev/ptmx", "/dev/kvm"
 #]
 #
 # RDMA migration requires the following extra files to be added to the list: