watchtower: remove dev tag from unit test files

Several watchtower unit tests were not being executed by make unit since
they require the dev tag to be passed in. All tests still pass.

watchtower/lookout/justice_descriptor_test.go

@@ -1,5 +1,3 @@
-// +build dev
-
 package lookout_test
 
 import (

watchtower/lookout/lookout_test.go

@@ -1,5 +1,3 @@
-// +build dev
-
 package lookout_test
 
 import (

watchtower/lookout/mock.go

@@ -1,5 +1,3 @@
-// +build dev
-
 package lookout
 
 import (