Remove underscore-rails gem

We now manage this dependency in Yarn.

Gemfile

@@ -207,9 +207,6 @@ gem 'kubeclient', '~> 2.2.0'
 # d3
 gem 'd3_rails', '~> 3.5.0'
-# underscore-rails
-gem 'underscore-rails', '~> 1.8.0'
-
 # Sanitize user input
 gem 'sanitize', '~> 2.0'
 gem 'babosa', '~> 1.0.2'

Gemfile.lock

@@ -899,7 +899,6 @@ GEM
     uglifier (2.7.2)
       execjs (>= 0.3.0)
       json (>= 1.8.0)
-    underscore-rails (1.8.3)
     unf (0.1.4)
       unf_ext
     unf_ext (0.0.7.2)
@@ -1163,7 +1162,6 @@ DEPENDENCIES
   truncato (~> 0.7.8)
   u2f (~> 0.2.1)
   uglifier (~> 2.7.2)
-  underscore-rails (~> 1.8.0)
   unf (~> 0.1.4)
   unicorn (~> 5.1.0)
   unicorn-worker-killer (~> 0.4.4)