Remove whenever gem

This was [added][1] when scheduling a Rake task to run every minute, and
evolved over time. However, all scheduling has since been [removed from
the Content Store code][2] but the gem was left behind

[1]: 796f217
[2]: 7a136e7

Gemfile

@@ -11,7 +11,6 @@ gem "pg"
 gem "plek"
 gem "rack-cache"
 gem "uuidtools"
-gem "whenever", require: false
 
 group :development, :test do
   gem "ci_reporter_rspec"

Gemfile.lock

@@ -94,7 +94,6 @@ GEM
       rack-test (>= 0.6.3)
       regexp_parser (>= 1.5, < 3.0)
       xpath (~> 3.2)
-    chronic (0.10.2)
     ci_reporter (2.0.0)
       builder (>= 2.1.2)
     ci_reporter_rspec (1.0.0)
@@ -667,8 +666,6 @@ GEM
     websocket-driver (0.7.6)
       websocket-extensions (>= 0.1.0)
     websocket-extensions (0.1.5)
-    whenever (1.0.0)
-      chronic (>= 0.6.3)
     xpath (3.2.0)
       nokogiri (~> 1.8)
     zeitwerk (2.7.1)
@@ -704,7 +701,6 @@ DEPENDENCIES
   timecop
   uuidtools
   webmock
-  whenever
 
 BUNDLED WITH
    2.3.22