labs: yocto: Untar the correct file to the NFS directory

This fixes a small typo in commit f6c905f.

Signed-off-by: Jef Driesen <[email protected]>

labs/yocto-advanced-configuration/yocto-advanced-configuration.tex

@@ -88,7 +88,7 @@ \section{Boot with the updated rootfs}
 previously created \code{/nfs} directory:
 \begin{verbatim}
 sudo tar xpf $BUILDDIR/tmp/deploy/images/beaglebone/\
-  core-image-minimal-beaglebone.rootfs.wic.xz -C /nfs
+  core-image-minimal-beaglebone.rootfs.tar.xz -C /nfs
 \end{verbatim}
 
 Then boot the board.