FAFT: Remove the legacy use_pyauto and use_faft arguments

These two arguements were introduced when ServoTest supported connecting
remote PyAuto and FAFT Client RPC servers. Now ServoTest only serves
FAFT Client, meaning that use_pyauto is always False and use_faft is always
True. So remove these arguments.

BUG=chrome-os-partner:21118;chromium-os:215491
TEST=Manual
Ran the affected test cases, firmware_FAFTSetup, on Spring and passed.

Change-Id: I5c740faddb97f81f052e720548bfce8a39b405e3
Reviewed-on: https://gerrit.chromium.org/gerrit/62641
Reviewed-by: Yusuf Mohsinally <mohsinally@chromium.org>
Reviewed-by: Richard Barnette <jrbarnette@chromium.org>
Commit-Queue: Tom Wai-Hong Tam <waihong@chromium.org>
Tested-by: Tom Wai-Hong Tam <waihong@chromium.org>
diff --git a/server/cros/servo_test.py b/server/cros/servo_test.py
index f8c9e82..72bd8c4 100644
--- a/server/cros/servo_test.py
+++ b/server/cros/servo_test.py
@@ -25,15 +25,9 @@
     _SSH_CONFIG = ('-o StrictHostKeyChecking=no '
                    '-o UserKnownHostsFile=/dev/null ')
 
-    def initialize(self, host, _, use_pyauto=False, use_faft=False):
+    def initialize(self, host):
         """Create a Servo object and install the dependency.
         """
-        # TODO(jrbarnette): Part of the incomplete refactoring:
-        # assert here that there are no legacy callers passing
-        # parameters for functionality that's been deprecated and
-        # removed.
-        assert use_faft and not use_pyauto
-
         self.servo = host.servo
         self.faft_client = None
         self._client = host