package/flex: fix typo in patch description

Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>

package/flex/0003-build-make-it-possible-to-disable-the-build-of-the-d.patch

@@ -4,7 +4,7 @@ Date: Fri, 29 Sep 2017 18:03:51 +0200
 Subject: [PATCH] build: make it possible to disable the build of the
  documentation
 
-When targetting embedded evices, the documentation is not needed.
+When targeting embedded devices, the documentation is not needed.
 
 Building the documentation default to whether the program is built.