DEV: Increase Capybara.default_max_wait_time on github actions (#19750)

Our working theory is that system tests on Github run on much less
powerful hardware as compared to running the tests on our work machines.
Hopefully, increasing the wait time now will help reduce some flakes
that we're seeing on Github.

.github/workflows/tests.yml

@@ -30,6 +30,7 @@ jobs:
       PGUSER: discourse
       PGPASSWORD: discourse
       USES_PARALLEL_DATABASES: ${{ matrix.build_type == 'backend' }}
+      CAPBYARA_DEFAULT_MAX_WAIT_TIME: 4
 
     strategy:
       fail-fast: false

spec/rails_helper.rb

@@ -245,6 +245,10 @@ RSpec.configure do |config|
       allow: [Webdrivers::Chromedriver.base_url]
     )
 
+    if ENV["CAPBYARA_DEFAULT_MAX_WAIT_TIME"].present?
+      Capybara.default_max_wait_time = ENV["CAPBYARA_DEFAULT_MAX_WAIT_TIME"].to_i
+    end
+
     Capybara.threadsafe = true
     Capybara.disable_animation = true