yocto: slides: remove '-b' bitbake flag

Not super easy to understand, not sure useful, and probably going to be
removed from bitbake.

Proposed-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>

slides/yocto-advanced/yocto-advanced.tex

@@ -322,8 +322,6 @@ \subsection{The power of BitBake}
       \item[\code{-f}] force the given task to be run by removing its
         stamp file
       \item[\code{world}] keyword for all recipes
-      \item[\code{-b <recipe>}] execute tasks from the given
-        \code{recipe} (without resolving dependencies).
     \end{description}
   \end{itemize}
 \end{frame}