Remove already executed tasks

These tasks were executed when upgading to version 0.19, 1.0.0-beta or
1.0.0.

spec/lib/tasks/db_spec.rb

@@ -1,15 +0,0 @@
-require "rails_helper"
-
-describe "rake db:pages" do
-  let :run_rake_task do
-    Rake.application.invoke_task("db:pages")
-  end
-
-  it "seeds the database with the default custom pages" do
-    SiteCustomization::Page.destroy_all
-    expect(SiteCustomization::Page.count).to be 0
-
-    run_rake_task
-    expect(SiteCustomization::Page.count).to be 7
-  end
-end