release: Zephyr 2.4.0

Set version to 2.4.0.

Signed-off-by: Maureen Helm <maureen.helm@nxp.com>
diff --git a/VERSION b/VERSION
index 3151da6..ccf86f6 100644
--- a/VERSION
+++ b/VERSION
@@ -2,4 +2,4 @@
 VERSION_MINOR = 4
 PATCHLEVEL = 0
 VERSION_TWEAK = 0
-EXTRAVERSION = rc3
+EXTRAVERSION =