Remove peek-sidekiq

The reason for removing this gem is that it's not being maintained
anymore. It uses `alias_method_chain` which is deprecated in rails 5
(and removed in 5.1), the issue is pending upstream (including
a fix) - https://github.com/suranyami/peek-sidekiq/issues/3 for a while.

Peek-sidekiq is used in performance bar for displaying sidekiq
statistics.

Gemfile

@@ -300,7 +300,6 @@ gem 'peek-mysql2', '~> 1.1.0', group: :mysql
 gem 'peek-pg', '~> 1.3.0', group: :postgres
 gem 'peek-rblineprof', '~> 0.2.0'
 gem 'peek-redis', '~> 1.2.0'
-gem 'peek-sidekiq', '~> 1.0.3'
 
 # Metrics
 group :metrics do

Gemfile.lock

@@ -605,10 +605,6 @@ GEM
       atomic (>= 1.0.0)
       peek
       redis
-    peek-sidekiq (1.0.3)
-      atomic (>= 1.0.0)
-      peek
-      sidekiq
     pg (0.18.4)
     po_to_json (1.0.1)
       json (>= 1.6.0)
@@ -1113,7 +1109,6 @@ DEPENDENCIES
   peek-pg (~> 1.3.0)
   peek-rblineprof (~> 0.2.0)
   peek-redis (~> 1.2.0)
-  peek-sidekiq (~> 1.0.3)
   pg (~> 0.18.2)
   premailer-rails (~> 1.9.7)
   prometheus-client-mmap (~> 0.9.4)

Gemfile.rails5.lock

@@ -609,10 +609,6 @@ GEM
       atomic (>= 1.0.0)
       peek
       redis
-    peek-sidekiq (1.0.3)
-      atomic (>= 1.0.0)
-      peek
-      sidekiq
     pg (0.18.4)
     po_to_json (1.0.1)
       json (>= 1.6.0)
@@ -1122,7 +1118,6 @@ DEPENDENCIES
   peek-pg (~> 1.3.0)
   peek-rblineprof (~> 0.2.0)
   peek-redis (~> 1.2.0)
-  peek-sidekiq (~> 1.0.3)
   pg (~> 0.18.2)
   premailer-rails (~> 1.9.7)
   prometheus-client-mmap (~> 0.9.4)

changelogs/unreleased/remove-sidekiq.yml

+---
+title: Remove sidekiq info from performance bar
+merge_request:
+author:
+type: removed

config/initializers/peek.rb

@@ -18,7 +18,6 @@ Peek.into PEEK_DB_VIEW
 Peek.into Peek::Views::Gitaly
 Peek.into Peek::Views::Rblineprof
 Peek.into Peek::Views::Redis
-Peek.into Peek::Views::Sidekiq
 Peek.into Peek::Views::GC
 
 # rubocop:disable Naming/ClassAndModuleCamelCase