Removed HOTPLUG=1 from the monitor hotplug rules.

Since udev didn't understand this key, it wasn't using it anyway.
This gets rid of the confusing error message in /var/log/messages.

BUG=chromium-os:13694
TEST=Plugged/unplugged a VGA monitor and made sure modes still switched.

...also, built with FEATURES=keepwork and checked this file:
/build/x86-mario/tmp/portage/sys-fs/udev-151-r6/work/udev-151/udev/udev-rules.c

...validated that the unknown key was actually being ignored by udev, so this doesn't change behavior (other than getting rid of the error message).

Review URL: http://codereview.chromium.org/6825017

Change-Id: I20fa098407299b0f0ff5cf06e95089fa0c8a7f5a
diff --git a/99-monitor-hotplug.rules b/99-monitor-hotplug.rules
index 77cefa7..37d6983 100644
--- a/99-monitor-hotplug.rules
+++ b/99-monitor-hotplug.rules
@@ -1,2 +1,2 @@
 # Reconfigure display output when the external monitor is [un]plugged.
-ACTION=="change", SUBSYSTEM=="drm", HOTPLUG=="1", RUN+="display-configure.sh"
+ACTION=="change", SUBSYSTEM=="drm", RUN+="display-configure.sh"