README: fix s/libwayland/libweston/ typo

Since one is (about to be) using libweston, they should check for it as
opposed to libwayland.

Silly copy/paste mistake that would have caused a lot of confusion.

Signed-off-by: Emil Velikov <emil.velikov@collabora.com>
Reviewed-by: Quentin Glidic <sardemff7+git@sardemff7.net>

README

@@ -133,7 +133,7 @@ weston_ham_sandwich(void);
 In order to use the said symbol, the one will have a similar code in their
 configure.ac:
 
-PKG_CHECK_MODULES(LIBWAYLAND, [libwayland-1 >= 1.1])
+PKG_CHECK_MODULES(LIBWESTON, [libweston-1 >= 1.1])
 AC_DEFINE(REQUIRE_LIBWESTON_API_VERSION, [0x0101])
 
 If the user is _not_ interested in forward compatibility, they can use 0xffff