Fix flaky test in releases_controller_spec.rb

Multiple release objects would be created in the test with the same tag
(v1.1.0), which caused random failures, depending on what the database
returned for Releases.find_by_tag!. Since there is no uniqueness
constraint, we fix this problem by changing the tag to a unique name.

Closes https://gitlab.com/gitlab-org/gitlab/issues/37372

spec/controllers/projects/releases_controller_spec.rb

@@ -167,7 +167,8 @@ describe Projects::ReleasesController do
   end
 
   describe 'GET #evidence' do
-    let!(:release) { create(:release, :with_evidence, project: project) }
+    let(:tag_name) { "v1.1.0-evidence" }
+    let!(:release) { create(:release, :with_evidence, project: project, tag: tag_name) }
     let(:tag) { CGI.escape(release.tag) }
     let(:format) { :json }