Buck: Adapt test rules to new acceptance-framework artifact

In I4cadf6616d acceptance-framework was exposed as new library
and Ie9e63de622 where //gerrit-acceptance-tests:lib with all its
transitive dependencies was added to plugin-api was partially
reverted.

Adapt test rules to add GERRIT_TESTS dependency. Note, that this
variable must be used, to support in tree and standalone Buck build
modes.

Change-Id: I77b4249c7fee1036cd38bc5e422c00f393a94adb
diff --git a/BUCK b/BUCK
index 1ea88ab..a93fedd 100644
--- a/BUCK
+++ b/BUCK
@@ -22,7 +22,7 @@
 java_library(
   name = 'its-base_tests-utils',
   srcs = TEST_UTIL_SRC,
-  deps = GERRIT_PLUGIN_API,
+  deps = GERRIT_PLUGIN_API + GERRIT_TESTS,
   visibility = ['PUBLIC'],
 )
 
@@ -34,7 +34,7 @@
   ),
   labels = ['its-base'],
   source_under_test = [':its-base__plugin'],
-  deps = GERRIT_PLUGIN_API + [
+  deps = GERRIT_PLUGIN_API + GERRIT_TESTS + [
     ':its-base__plugin',
     ':its-base_tests-utils',
   ],