Stop validating factories in specs

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

spec/models/resource_spec.rb

@@ -24,10 +24,6 @@ describe Resource do
 
   it { is_expected.to allow_value(0).for(:quantity) }
 
-  it 'has a valid factory' do
-    expect(build(:resource)).to be_valid
-  end
-
   it 'is not valid with used greater than quantity' do
     resource.used = resource.quantity + 1
     expect(resource.valid?).to eq false