Remove legacy remote authentication code in Bazel mode

Atest no longer requires authentication scripts now that Bazel supports
credential helpers.

See
https://bazel.build/reference/command-line-reference#flag--experimental_credential_helper for more details.

Bug: 254607314
Test: atest --host atest_unittests
Change-Id: Ica4026109abd1cb73c784e31e6c8abb965888d27
diff --git a/atest/bazel_mode.py b/atest/bazel_mode.py
index 2d5c528..dbaaed9 100644
--- a/atest/bazel_mode.py
+++ b/atest/bazel_mode.py
@@ -1347,13 +1347,7 @@
             feature, 'ATEST_BAZEL_REMOTE_CONFIG')
         if not remote_config:
             return []
-
-        args = [f'--config={remote_config}']
-        auth_script = self.env.get('ATEST_BAZEL_REMOTE_AUTH_SCRIPT')
-        if auth_script:
-            args.extend(self._get_auth_args(auth_script))
-
-        return args
+        return [f'--config={remote_config}']
 
     def host_env_check(self):
         """Check that host env has everything we need.