Remove unused gems and yarn packages.

Gemfile.lock

@@ -171,10 +171,6 @@ GEM
       concurrent-ruby (~> 1.0)
     ipaddress_2 (0.13.0)
     jmespath (1.4.0)
-    jquery-rails (4.3.5)
-      rails-dom-testing (>= 1, < 3)
-      railties (>= 4.2.0)
-      thor (>= 0.14, < 2.0)
     json (2.3.0)
     jwt (2.2.1)
     kgio (2.11.3)
@@ -299,7 +295,6 @@ GEM
     responders (3.0.1)
       actionpack (>= 5.0)
       railties (>= 5.0)
-    retriable (3.1.2)
     rexml (3.2.4)
     rubocop (0.86.0)
       parallel (~> 1.10)
@@ -415,7 +410,6 @@ DEPENDENCIES
   flamegraph
   http
   ipaddress_2
-  jquery-rails
   listen
   mail
   memoist
@@ -442,7 +436,6 @@ DEPENDENCIES
   redis
   request_store
   responders
-  retriable
   rubocop
   rubocop-rails
   ruby-vips