Update git submodules

* Update tools/repohooks from branch 'master'
  to 6078fd9aa2f5dd7241b63e495bb4e3d7210be1a3
  - README: improve config file docs
    
    Bug: None
    Test: read in gitiles
    Change-Id: If931b94cfd2235f5a7b9e946c0da3e5099455149
    
diff --git a/tools/repohooks b/tools/repohooks
index 828a0ee..6078fd9 160000
--- a/tools/repohooks
+++ b/tools/repohooks
@@ -1 +1 @@
-Subproject commit 828a0ee68d15b13544494ac057ff40ae645ddf18
+Subproject commit 6078fd9aa2f5dd7241b63e495bb4e3d7210be1a3