chore: remove build badges

b/468377909

Author: suztomo

README.md

@@ -1,8 +1,5 @@
 ## Ruby docs samples
 
-Ruby 2.4: [![Kokoro](https://storage.googleapis.com/cloud-devrel-public/ruby-docs-samples/badges/ruby2.4.svg)](https://storage.googleapis.com/cloud-devrel-public/ruby-docs-samples/badges/ruby2.4.html)
-Ruby 2.5: [![Kokoro](https://storage.googleapis.com/cloud-devrel-public/ruby-docs-samples/badges/ruby2.5.svg)](https://storage.googleapis.com/cloud-devrel-public/ruby-docs-samples/badges/ruby2.5.html)
-
 This repository holds samples used in the ruby documentation on
 cloud.google.com.