lint: fix superfluous parenthesis

Newer pylint catches warnings like:
C:1950, 0: Unnecessary parens after 'if' keyword (superfluous-parens)

BUG=chromium:431514
TEST=`./cbuildbot/run_tests` passes
TEST=`cros lint` no longer complains about superfluous-parens

Change-Id: I47f901f8ceb06402e3c2e83303b7be38390ae535
Reviewed-on: https://chromium-review.googlesource.com/229510
Reviewed-by: Gabe Black <gabeblack@chromium.org>
Commit-Queue: Mike Frysinger <vapier@chromium.org>
Tested-by: Mike Frysinger <vapier@chromium.org>
diff --git a/scripts/cros_setup_toolchains.py b/scripts/cros_setup_toolchains.py
index f0bdb95..f79d5cc 100644
--- a/scripts/cros_setup_toolchains.py
+++ b/scripts/cros_setup_toolchains.py
@@ -205,8 +205,8 @@
   # Portage package:
   pn = conf[package + '_pn']
   # Final package name:
-  assert(category)
-  assert(pn)
+  assert category
+  assert pn
   return '%s/%s' % (category, pn)