release: bump to 1.13.0-rc3

Update version.

Signed-off-by: Anas Nashif <anas.nashif@intel.com>
diff --git a/VERSION b/VERSION
index be7c0da..59d5ada 100644
--- a/VERSION
+++ b/VERSION
@@ -2,4 +2,4 @@
 VERSION_MINOR = 13
 PATCHLEVEL = 0
 VERSION_TWEAK = 0
-EXTRAVERSION = rc2
+EXTRAVERSION = rc3