Resolve "Imports fail in 14.5.2 fail with HTTParty::UnsupportedURIScheme error"

See https://gitlab.com/gitlab-org/gitlab/-/merge_requests/78479

Changelog: fixed

app/services/import/validate_remote_git_endpoint_service.rb

@@ -23,6 +23,8 @@ module Import
       return ServiceResponse.error(message: "#{@params[:url]} is not a valid URL") unless uri
+      return ServiceResponse.success if uri.scheme == 'git'
+
       uri.fragment = nil
       url = Gitlab::Utils.append_path(uri.to_s, "/info/refs?service=#{GIT_SERVICE_NAME}")

spec/services/import/validate_remote_git_endpoint_service_spec.rb

@@ -24,6 +24,17 @@ RSpec.describe Import::ValidateRemoteGitEndpointService do
       expect(Gitlab::HTTP).to have_received(:get).with(endpoint_url, basic_auth: nil, stream_body: true, follow_redirects: false)
     end
+    context 'when uri is using git:// protocol' do
+      subject { described_class.new(url: 'git://demo.host/repo')}
+
+      it 'returns success' do
+        result = subject.execute
+
+        expect(result).to be_a(ServiceResponse)
+        expect(result.success?).to be(true)
+      end
+    end
+
     context 'when receiving HTTP response' do
       subject { described_class.new(url: base_url) }