Fix Picture and Attachment specs for MySQL

These specs would previously fail as their element's updated at would
not, actually, be `3.hours.ago`, but `Time.current - $TESTRUNTIME`. This
is more explicit with setting the column, and fixes the specs.

spec/models/alchemy/attachment_spec.rb

@@ -36,13 +36,12 @@ module Alchemy
         let(:attachment) { create(:alchemy_attachment) }
 
         let(:content) do
-          create(:alchemy_content, :essence_file).tap do |content|
-            content.element.update_column(:updated_at, 3.hours.ago)
-          end
+          create(:alchemy_content, :essence_file)
         end
 
         before do
           content.essence.update(attachment: attachment)
+          content.element.update_column(:updated_at, 3.hours.ago)
         end
 
         it "touches elements" do

spec/models/alchemy/picture_spec.rb

@@ -512,13 +512,12 @@ module Alchemy
         let(:picture) { create(:alchemy_picture) }
 
         let(:content) do
-          create(:alchemy_content, :essence_picture).tap do |content|
-            content.element.update_column(:updated_at, 3.hours.ago)
-          end
+          create(:alchemy_content, :essence_picture)
         end
 
         before do
           content.essence.update(picture: picture)
+          content.element.update_column(:updated_at, 3.hours.ago)
         end
 
         it "touches elements" do