clean up hidden calls to SessionPool.create

spec/mongo/session/session_pool_spec.rb

@@ -17,21 +17,6 @@
     end
   end
 
-  describe '.create' do
-
-    let!(:pool) do
-      described_class.create(cluster)
-    end
-
-    it 'creates a session pool' do
-      expect(pool).to be_a(Mongo::Session::SessionPool)
-    end
-
-    it 'adds the pool as an instance variable on the cluster' do
-      expect(cluster.session_pool).to eq(pool)
-    end
-  end
-
   describe '#initialize' do
 
     let(:pool) do
@@ -181,7 +166,7 @@
   describe '#end_sessions' do
 
     let(:pool) do
-      described_class.create(client.cluster)
+      described_class.new(client.cluster)
     end
 
     let!(:session_a) do