Drop skylight, we already support sentry

Gemfile

@@ -186,9 +186,6 @@ gem 'sprockets-rails'
 # for multiple speakers select on proposal/event forms
 gem 'selectize-rails'
 
-# For collecting performance data
-gem 'skylight'
-
 # memcached binary connector
 gem 'dalli'
 

Gemfile.lock

@@ -543,8 +543,6 @@ GEM
       simplecov (~> 0.19)
     simplecov-html (0.12.3)
     simplecov_json_formatter (0.1.4)
-    skylight (6.0.4)
-      activesupport (>= 5.2.0)
     snaky_hash (2.0.1)
       hashie
       version_gem (~> 1.1, >= 1.1.1)
@@ -697,7 +695,6 @@ DEPENDENCIES
   sentry-rails
   shoulda-matchers
   simplecov-cobertura
-  skylight
   sprockets-rails
   stripe
   stripe-ruby-mock (~> 3.1.0.rc3)

app/views/layouts/application.html.haml

@@ -46,8 +46,5 @@
             You can run, copy, distribute, study, change and improve it.
             The source code and the developers are on
             #{link_to "GitHub", "https://github.com/openSUSE/osem"}.
-            - if ENV.fetch('SKYLIGHT_PUBLIC_DASHBOARD_URL', nil)
-              Performance data is available on
-              #{link_to "Skylight", ENV["SKYLIGHT_PUBLIC_DASHBOARD_URL"]}.
     = yield :script_body
     = yield :charts_js

dotenv.example

@@ -105,10 +105,6 @@
 # Force all access to the app over SSL, use Strict-Transport-Security, and use secure cookies.
 # FORCE_SSL=true
 
-# Your skylight.io keys
-# SKYLIGHT_AUTHENTICATION=1234
-# SKYLIGHT_PUBLIC_DASHBOARD_URL='https://oss.skylight.io/app/applications/xxxxxxxxxxxx'
-
 # How should browser tests be performed?
 # For headless Chrome (default):
 # OSEM_TEST_DRIVER=chrome_headless