Add FileHistoryWebLink to plugin documentation

Change-Id: I96eb03c2cdc227a2a44f626c50b53499e28c329c
Signed-off-by: Edwin Kempin <ekempin@google.com>

Documentation/dev-plugins.txt

diff --git a/Documentation/dev-plugins.txt b/Documentation/dev-plugins.txt
index dbaa3c1..429aa92 100644
--- a/Documentation/dev-plugins.txt
+++ b/Documentation/dev-plugins.txt
@@ -2065,6 +2065,8 @@
 
 BranchWebLinks will appear in the branch list in the last column.
 
+FileHistoryWebLinks will appear on the access rights screen.
+
 [[lfs-extension]]
 == LFS Storage Plugins