Remove unnecessary clear_stubs calls

spec/lib/gitlab/git/repository_spec.rb

@@ -5,11 +5,6 @@ describe Gitlab::Git::Repository, seed_helper: true do
 
   let(:repository) { Gitlab::Git::Repository.new('default', TEST_REPO_PATH) }
 
-  after do
-    # Prevent cached stubs (gRPC connection objects) from poisoning tests.
-    Gitlab::GitalyClient.clear_stubs!
-  end
-
   describe "Respond to" do
     subject { repository }
 

spec/lib/gitlab/gitaly_client/ref_spec.rb

@@ -6,13 +6,6 @@ describe Gitlab::GitalyClient::Ref do
   let(:relative_path) { project.path_with_namespace + '.git' }
   let(:client) { described_class.new(project.repository) }
 
-  after do
-    # When we say `expect_any_instance_of(Gitaly::Ref::Stub)` a double is created,
-    # and because GitalyClient shares stubs these will get passed from example to
-    # example, which will cause an error, so we clean the stubs after each example.
-    Gitlab::GitalyClient.clear_stubs!
-  end
-
   describe '#branch_names' do
     it 'sends a find_all_branch_names message' do
       expect_any_instance_of(Gitaly::Ref::Stub)