Update Backlinks in Standard.md

[BolajiAyodeji]

Fixes # . (N/A)

Changes proposed in this pull request:

This PR updates the links to the full license list and definition of PII data in the standard.md file to the updated Wiki pages.

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