Update contrast-finder_utf8_es.properties

[davidjr82]

Updated the missing translations. Changed the translation "criterios de validez" in favor of "criterios de éxito" because it is the commonly accepted term in Spanish.

I verified my work is based on develop branch

• [x] yes, keep going
• [ ] hum... no, because:
  • [ ] I don't understand the develop / branch / trees / flowers stuff !
  • [ ] I need help. No worries, we will help you :)
  • [ ] I'm a super-karma-powered contributor, will not tick this box and will rebase my PR within seconds (thanks :) )

Purpose of this Pull Request?

Update spanish translation

Where should the reviewer start its review?

File /webapp/src/main/resources/i18n/contrast-finder_utf8_es.properties

What are the related issues?

Issue #244