Audit GitHub Stamp to make it more clear that only unique commit days are counted

[lebraat]

User Story:

As a user
I want to better understand the criteria of the GitHub stamp
So that I can know how I'm trending towards qualifying for the Stamp

Acceptance Criteria

GIVEN a user who doesn't fully qualify for the GitHub stamp
WHEN they try to verify the stamp
THEN they receive error messages and other details that help them identify how to become eligible for the Stamp.

1. Update the language in error messages from 'contributions' to 'unique commits' (since we changed the requirements of the stamp a few months ago)
2. Pair with Daniel to improve the app he's working on to make sure it matches the Stamp so we can use with our support team (and possibly users) if we need deeper support / understanding on the issues.

Product & Design Links:

Current Errors:
"error": "You have contributed on 0 days, the minimum for this stamp is 30 days. Some commits were ignored because they ocurred before the Github repo or user creation."

"error": "You have contributed on 0 days, the minimum for this stamp is 60 days. Some commits were ignored because they ocurred before the Github repo or user creation."

"error": "You have contributed on 0 days, the minimum for this stamp is 120 days. Some commits were ignored because they ocurred before the Github repo or user creation.

Change to the following: (bold words are additions / changes)
"error": "You have contributed on 0 days, the minimum for this stamp is 30 days. Some unique commits were ignored because they occurred before the Github repo or user creation."

"error": "You have contributed on 0 days, the minimum for this stamp is 60 days. Some unique commits were ignored because they occurred before the Github repo or user creation."

"error": "You have contributed on 0 days, the minimum for this stamp is 120 days. Some unique commits were ignored because they occurred before the Github repo or user creation.

If there are other stamp errors for Github that say "contributions" we should update this to "Unique commit days"