Bump selenium-webdriver from 3.142.5 to 3.142.6 in /backend

Bumps [selenium-webdriver](https://github.com/SeleniumHQ/selenium) from 3.142.5 to 3.142.6.
- [Release notes](https://github.com/SeleniumHQ/selenium/releases)
- [Changelog](https://github.com/SeleniumHQ/selenium/blob/master/rb/CHANGES)
- [Commits](https://github.com/SeleniumHQ/selenium/commits)

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

Author: dependabot-preview[bot]

backend/Gemfile.lock

@@ -71,8 +71,7 @@ GEM
       rack-test (>= 0.6.3)
       regexp_parser (~> 1.5)
       xpath (~> 3.2)
-    childprocess (2.0.0)
-      rake (< 13.0)
+    childprocess (3.0.0)
     concurrent-ruby (1.1.5)
     crass (1.0.4)
     erubi (1.8.0)
@@ -136,15 +135,15 @@ GEM
       method_source
       rake (>= 0.8.7)
       thor (>= 0.20.3, < 2.0)
-    rake (12.3.3)
+    rake (13.0.0)
     rb-fsevent (0.10.3)
     rb-inotify (0.9.10)
       ffi (>= 0.5.0, < 2)
     regexp_parser (1.6.0)
     ruby_dep (1.5.0)
     rubyzip (2.0.0)
-    selenium-webdriver (3.142.5)
-      childprocess (>= 0.5, < 3.0)
+    selenium-webdriver (3.142.6)
+      childprocess (>= 0.5, < 4.0)
       rubyzip (>= 1.2.2)
     spring (2.1.0)
     spring-watcher-listen (2.0.1)