[doc] Frama-C does not contain non-free code, this check is obsolete

doc/release/validation.tex

@@ -134,7 +134,9 @@ Check that these artifacts are as expected. In particular:
   \item Check versions in manuals
   \item Tarball
     \begin{itemize}
-      \item Check that no non-free components are distributed
+      \item Check that no non-free components are distributed (note: unless
+      someone inadvertently added non-free code, \FramaC does not contain any,
+      this check is obsolete).
       \item Check that no \texttt{/home/user} path can be found in the distribution,
       \item Build and test
         \begin{itemize}