Update standard help text to match the current review process

[ricardomiron]

Changes proposed in this pull request:

The previous process allowed anyone to nominate a digital solution for DPG recognition and required certain indicators to be given by someone authorized to speak on behalf of the project. With the deprecation of "nominees" within the process, it is now required that all information is submitted by an authorized representative of the project.

Propagation of Changes

Identify where the following proposed changes need to be propagated and include the relevant pull request where appropriate:

• The DPGA website contains https://digitalpublicgoods.net/standard/ which needs to be updated manually to match the contents of standard.md.
• The DPGA website also contains the submission guide which needs to be updated manually.
• The DPGAlliance/publicgoods-candidates repository needs the following to be updated:
  • the nominee-schema.json
  • the screening-schema.json
  • propagate any changes to all encoded nominees and digital public goods.
  • Link to the corresponding pull request: unicef/publicgoods-candidates#
• The Submission Form through the unicef/publicgoods-submission repository, and its corresponding schema.js
• The Eligibility Form through the unicef/publicgoods-scripts repository, by editing quizQuestions.js