Remove archiving and endorsement policies

[ricardomiron]

Changes proposed in this pull request:

• Removes archiving policy, which now lives in the DPG Wiki
• Removes endorsements as it is no longer maintained or active.

Propagation of Changes

Identify where of the following the 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 matching the contents of standard.md.
• The DPGA website also contains the submission guide which needs to be updated manually.
• The DPG application webapp admin panel which will be updated manually.
• The Eligibility Form through the unicef/publicgoods-scripts repository, by editing quizQuestions.js