autotest: Update site-tests dependencies to 'servo_state:WORKING'

BUG=chromium:1045191
TEST=presubmit,unittest

Change-Id: I598c55c37faa58d566142fce9fff2653e4e18bdd
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/autotest/+/2040702
Tested-by: Otabek Kasimov <[email protected]>
Reviewed-by: Tom Hughes <[email protected]>
Reviewed-by: Xixuan Wu <[email protected]>
Reviewed-by: Allen Li <[email protected]>
Commit-Queue: Otabek Kasimov <[email protected]>
Auto-Submit: Otabek Kasimov <[email protected]>
diff --git a/docs/best-practices.md b/docs/best-practices.md
index fd36f8b..a4f1752 100644
--- a/docs/best-practices.md
+++ b/docs/best-practices.md
@@ -271,8 +271,10 @@
 
 ```
 # ... Standard boilerplate variable assignments...
-DEPENDENCIES = "servo"
+DEPENDENCIES = "servo_state:WORKING"
 # ... more standard boilerplate...
+# servo_state:WORKING - servo is present and can provide required functionality
+# servo_state:BROKEN - servo is present but cannot provide required functionality
 
 args_dict = utils.args_to_dict(args)
 servo_args = hosts.SiteHost.get_servo_arguments(args_dict)