qemu-doc: do not refer to years-old version numbers

Reviewed-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

qemu-doc.texi

@@ -386,11 +386,9 @@ CPU registers by prefixing them with @emph{$}.
 @node disk_images
 @section Disk Images
 
-Since version 0.6.1, QEMU supports many disk image formats, including
-growable disk images (their size increase as non empty sectors are
-written), compressed and encrypted disk images. Version 0.8.3 added
-the new qcow2 disk image format which is essential to support VM
-snapshots.
+QEMU supports many disk image formats, including growable disk images
+(their size increase as non empty sectors are written), compressed and
+encrypted disk images.
 
 @menu
 * disk_images_quickstart::    Quick start for disk image creation