doc: Kernel is now 4.19

Signed-off-by: Stewart Smith <stewart@linux.ibm.com>
diff --git a/doc/process/KernelTree.rst b/doc/process/KernelTree.rst
index 87ec71c..1d6832d 100644
--- a/doc/process/KernelTree.rst
+++ b/doc/process/KernelTree.rst
@@ -1,7 +1,7 @@
 op-build Linux Kernel
 =====================
 
-The skiroot/Petitboot kernel is currently based on the 4.17 series.
+The skiroot/Petitboot kernel is currently based on the 4.19 series.
 
 Submitting a patch
 ------------------