fix(apparmor): Fix accessibility DBus access

AppArmor denies access to a11y:
```
Jan 26 15:23:31 vincas-ubuntu1804 dbus-daemon: apparmor="DENIED"
operation="dbus_method_call"  bus="accessibility"
path="/org/freedesktop/DBus" interface="org.freedesktop.DBus"
member="Hello" mask="send" name="org.freedesktop.DBus" pid=8011
label="qtox" peer_label="unconfined"

Jan 26 15:23:31 vincas-ubuntu1804 dbus-daemon[1474]: apparmor="DENIED"
operation="dbus_method_call"  bus="session" path="/org/a11y/bus"
interface="org.freedesktop.DBus.Properties" member="Get" mask="send"
name="org.a11y.Bus" pid=8011 label="qtox" peer_pid=1620
peer_label="unconfined"
```

Include dbus-accessibility abstraction and one addition dbus rule to fix
denies.

security/apparmor/2.12.1/usr.bin.qtox

@@ -8,6 +8,7 @@
 profile qtox /usr{,/local}/bin/qtox {
   #include <abstractions/audio>
   #include <abstractions/base>
+  #include <abstractions/dbus-accessibility>
   #include <abstractions/dbus-session-strict>
   #include <abstractions/dri-enumerate>
   #include <abstractions/gnome>
@@ -38,6 +39,15 @@ profile qtox /usr{,/local}/bin/qtox {
   network tcp,
   network udp,
 
+  # DBus
+
+  dbus send
+    bus=session
+    path=/org/a11y/bus
+    interface=org.freedesktop.DBus.Properties
+    member=Get
+    peer=(label=unconfined),
+
   # System files
 
   @{qtox_additional_rw_dirs}/ r,

security/apparmor/2.13.2/usr.bin.qtox

@@ -8,6 +8,7 @@
 profile qtox /usr{,/local}/bin/qtox {
   #include <abstractions/audio>
   #include <abstractions/base>
+  #include <abstractions/dbus-accessibility>
   #include <abstractions/dbus-session-strict>
   #include <abstractions/dri-enumerate>
   #include <abstractions/gnome>
@@ -44,6 +45,15 @@ profile qtox /usr{,/local}/bin/qtox {
   network tcp,
   network udp,
 
+  # DBus
+
+  dbus send
+    bus=session
+    path=/org/a11y/bus
+    interface=org.freedesktop.DBus.Properties
+    member=Get
+    peer=(label=unconfined),
+
   # System files
 
   @{qtox_additional_rw_dirs}/ r,