Remove test that is already done in unit test

This test is not asserting against anything on the page.
There is already coverage for this in the
volunteers model spec.

Author: stefannibrasil

spec/system/volunteers/invite_spec.rb

@@ -200,15 +200,4 @@
       expect(page).to have_selector(".alert", text: "Sorry, you are not authorized to perform this action.")
     end
   end
-
-  describe "invitation expiration" do
-    let(:volunteer) { create(:volunteer, casa_org: organization) }
-
-    it "volunteers have invitation valid for 1 year" do
-      volunteer.invite!(admin)
-
-      # Check that volunteer model has correct invitation period
-      expect(Volunteer.invite_for).to eq(1.year)
-    end
-  end
 end