Stop validating factories in specs

We do validate all of them in a before(:suite) already.

spec/models/sponsor_spec.rb

@@ -4,10 +4,6 @@ require 'spec_helper'
 
 describe Sponsor do
   describe 'validations' do
-    it 'has a valid factory' do
-      expect(build(:sponsor)).to be_valid
-    end
-
     it 'is not valid without a name' do
       should validate_presence_of(:name)
     end