Remove old specs that are no longer relevant

These specs originate from this one:
fe90e05#diff-139363042a1d27e5830373d80deb5a2f8e7afcb68e28be55a73ffbd587517c0dR55-R57
But it was implemented in a wrong way (without calling #image=). Also this assumption doesn't hold true after #2658.

spec/orm/activerecord_spec.rb

@@ -197,10 +197,6 @@ def reset_class(class_name)
         expect(@event.image).to be_an_instance_of(@uploader)
       end
 
-      it "should write nothing to the database, to prevent overridden filenames to fail because of unassigned attributes" do
-        expect(@event[:image]).to be_nil
-      end
-
       it "should copy a file into the cache directory" do
         @event.image = stub_file('test.jpeg')
         expect(@event.image.current_path).to match(%r(^#{public_path('uploads/tmp')}))
@@ -1291,10 +1287,6 @@ def filename
         expect(@event.images[0]).to be_an_instance_of(@uploader)
       end
 
-      it "should write nothing to the database, to prevent overridden filenames to fail because of unassigned attributes" do
-        expect(@event[:images]).to be_nil
-      end
-
       it "should copy a file into into the cache directory" do
         @event.images = [stub_file('test.jpeg')]
         expect(@event.images[0].current_path).to match(%r(^#{public_path('uploads/tmp')}))