Remove unnecessary specs when PostgreSQL FDW is not enabled

Since GitLab 12.0 foreign data wrapper (FDW) is a hard
requirement.

ee/spec/support/helpers/ee/geo_helpers.rb

@@ -21,14 +21,6 @@ module EE
       allow(::Gitlab::Geo).to receive(:secondary?).and_return(true)
     end
 
-    def stub_fdw(value)
-      allow(::Gitlab::Geo::Fdw).to receive(:enabled?).and_return(value)
-    end
-
-    def stub_fdw_disabled
-      stub_fdw(false)
-    end
-
     def stub_selective_sync(node, value)
       allow(node).to receive(:selective_sync?).and_return(value)
     end

ee/spec/workers/geo/repository_shard_sync_worker_spec.rb

@@ -13,7 +13,7 @@ describe Geo::RepositoryShardSyncWorker, :geo, :geo_fdw, :clean_gitlab_redis_cac
     stub_current_geo_node(secondary)
   end
 
-  shared_examples '#perform' do
+  describe '#perform' do
     let!(:restricted_group) { create(:group) }
 
     let!(:unsynced_project_in_restricted_group) { create(:project, group: restricted_group) }
@@ -289,16 +289,4 @@ describe Geo::RepositoryShardSyncWorker, :geo, :geo_fdw, :clean_gitlab_redis_cac
       end
     end
   end
-
-  describe 'when PostgreSQL FDW is available', :geo, :geo_fdw do
-    it_behaves_like '#perform'
-  end
-
-  describe 'when PostgreSQL FDW is not enabled', :geo do
-    before do
-      allow(Gitlab::Geo::Fdw).to receive(:enabled?).and_return(false)
-    end
-
-    it_behaves_like '#perform'
-  end
 end

ee/spec/workers/geo/repository_verification/secondary/shard_worker_spec.rb

@@ -11,7 +11,6 @@ describe Geo::RepositoryVerification::Secondary::ShardWorker, :geo, :geo_fdw, :r
 
   before do
     stub_current_geo_node(secondary)
-    stub_fdw_disabled
   end
 
   describe '#perform' do