Bump rake from 12.1.0 to 12.3.3 in /service_broker

Bumps [rake](https://github.com/ruby/rake) from 12.1.0 to 12.3.3.
- [Release notes](https://github.com/ruby/rake/releases)
- [Changelog](https://github.com/ruby/rake/blob/master/History.rdoc)
- [Commits](ruby/rake@v12.1.0...v12.3.3)

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

Author: dependabot[bot]

service_broker/Gemfile.lock

@@ -28,7 +28,7 @@ GEM
       rack
     rack-test (0.7.0)
       rack (>= 1.0, < 3)
-    rake (12.1.0)
+    rake (12.3.3)
     safe_yaml (1.0.4)
     sawyer (0.8.1)
       addressable (>= 2.3.5, < 2.6)