Bump selenium-webdriver from 3.11.0 to 3.12.0

Bumps [selenium-webdriver](https://github.com/SeleniumHQ/selenium) from 3.11.0 to 3.12.0.
- [Release notes](https://github.com/SeleniumHQ/selenium/releases)
- [Changelog](https://github.com/SeleniumHQ/selenium/blob/master/rb/CHANGES)
- [Commits](SeleniumHQ/selenium@selenium-3.11.0...selenium-3.12.0)

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

Gemfile.lock

@@ -296,7 +296,7 @@ GEM
     screenshot_opener (0.1.0)
       actionpack (>= 5.1.0)
       activesupport (>= 5.1.0)
-    selenium-webdriver (3.11.0)
+    selenium-webdriver (3.12.0)
       childprocess (~> 0.5)
       rubyzip (~> 1.2)
     simplecov (0.14.1)