kernel: intro: sources: Don't mention realtime as sub-community dev tree

Mentionning real-time in the list of sub-community treeis is misleading,
as we state these trees aren't meant to be used in products.

Realtime is a bit different, as there are stable trees with RT that
are maintained, containing both stable fixes from linux-stable and
fixes to the RT patch.

Instead, mention other dev trees for core subsystems.

Signed-off-by: Maxime Chevallier <[email protected]>

slides/kernel-intro-sources/kernel-intro-sources.tex

@@ -143,7 +143,7 @@ \subsection{Linux kernel sources}
     \begin{itemize}
     \item Architecture communities (ARM, MIPS, PowerPC, etc)
     \item Device drivers communities (I2C, SPI, USB, PCI, network, etc)
-    \item Other communities (real-time, etc)
+    \item Other communities (filesystems, memory-management, scheduling, etc)
     \item Not suitable to be used in products
     \end{itemize}
   \end{itemize}