regex to check nginx does not provide version

spec/docker_runtime/runtime_spec.rb

@@ -120,7 +120,7 @@ describe 'passbolt_api service' do
     end
 
     it 'hides nginx version' do
-      expect(command("#{curl} | grep 'Server:'").stdout).to match 'Server: nginx'
+      expect(command("#{curl} | grep 'Server:'").stdout).to match /^Server: nginx$/
     end
   end