Bump faker from 1.9.6 to 2.1.0 in /WcaOnRails

Bumps [faker](https://github.com/stympy/faker) from 1.9.6 to 2.1.0.
- [Release notes](https://github.com/stympy/faker/releases)
- [Changelog](https://github.com/stympy/faker/blob/master/CHANGELOG.md)
- [Commits](faker-ruby/faker@1.9.6...v2.1.0)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

There were some breaking changes introduced in this version of `faker`
(see https://github.com/faker-ruby/faker/blob/2.0/CHANGELOG.md#v200-2019-31-07) @jfly updated the one place where we invoke a `faker` method
with some arguments to use a keyword argument instead.

WcaOnRails/Gemfile.lock

@@ -204,7 +204,7 @@ GEM
     factory_bot_rails (5.0.2)
       factory_bot (~> 5.0.2)
       railties (>= 4.2.0)
-    faker (1.9.6)
+    faker (2.1.0)
       i18n (>= 0.7)
     faraday (0.15.4)
       multipart-post (>= 1.2, < 3)

WcaOnRails/spec/factories/polls.rb

@@ -23,6 +23,6 @@
 
 FactoryBot.define do
   factory :poll_option do
-    description { Faker::Lorem.words(4).join }
+    description { Faker::Lorem.words(number: 4).join }
   end
 end