ci: Bump RFL kernel

ci/test.sh

diff --git a/ci/test.sh b/ci/test.sh
index da7ef8d..8dedb72 100755
--- a/ci/test.sh
+++ b/ci/test.sh
@@ -99,7 +99,7 @@
   # and each update should only contain this change.
   #
   # Both commit hashes and tags are supported.
-  LINUX_VERSION=v6.18-rc3
+  LINUX_VERSION=v6.19
 
   # Download Linux at a specific commit
   mkdir -p linux