Update Linux to 5.6

Test Plan: Covered by existing tests.

X-Origin-Diff: phab/D458
GitOrigin-RevId: ebc83b17a0bcf66997d65763d8ff852a2613887c
diff --git a/WORKSPACE b/WORKSPACE
index bbd126a..fce9c7f 100644
--- a/WORKSPACE
+++ b/WORKSPACE
@@ -95,7 +95,7 @@
 
 linux_external(
     name = "linux",
-    version = "5.4.7",
+    version = "5.6",
 )
 
 load("//third_party/edk2:external.bzl", "edk2_external")