docs: Fix minimum supported version

We already have that in the code (commit c1bc9c66), we just forgot to
mention that in the docs.
Signed-off-by: NMartin Kletzander <mkletzan@redhat.com>

docs/drvqemu.html.in

@@ -8,7 +8,7 @@
 
     <p>
       The libvirt KVM/QEMU driver can manage any QEMU emulator from
-      version 0.12.0 or later.
+      version 1.5.0 or later.
     </p>
 
     <h2><a id="project">Project Links</a></h2>