docs: fix libvirt version for vram64 in formatdomain.html.in

Signed-off-by: NPavel Hrdina <phrdina@redhat.com>

docs/formatdomain.html.in

@@ -5200,7 +5200,7 @@ qemu-kvm -net nic,model=? /dev/null
           two as <code>vram</code>. There is also optional attribute
           <code>vgamem</code> (<span class="since">since 1.2.11</span>) to set
           the size of VGA framebuffer for fallback mode of QXL device.
-          Attribute <code>vram64</code> (<span class="since">since 1.3.2</span>)
+          Attribute <code>vram64</code> (<span class="since">since 1.3.3</span>)
           extends secondary bar and makes it addressable as 64bit memory.
         </p>
       </dd>