CORE-266: remove group notification v1

[davidangb]

in the notifications library, deletes GroupAccessRequestNotification, which was deprecated in 0.10.

Context of the overall rollout plan to adopt the SendGrid v3 APIs by February 10:

1. [DONE] CORE-266: all email notifications use a single Reply-To address thurloe#369, which ensures all email notifications use a single reply-to~
2. [DONE] CORE-235, CORE-266: re-enable sendgrid-java 4.10.3 and corresponding syntax changes thurloe#368, which adopts the latest sendgrid-java and v3 APIs
3. [DONE] Modify workbench-libs to deprecate the GroupAccessRequestNotification used by Sam which allows multiple reply-tos; provide a replacement GroupAccessRequestNotificationV2 that only allows a single reply-to. See CORE-266: enforce a single reply-to address on group-access-request notifications #1717 (this PR)
4. [DONE] Support the new GroupAccessRequestNotificationV2 model in Thurloe. See CORE-235: support GroupAccessRequestNotificationV2 notifications thurloe#372
5. CORE-266: use GroupAccessRequestNotificationV2 sam#1627 Use the new GroupAccessRequestNotificationV2 model in Sam. After this step, Thurloe would no longer ignore the reply-to value sent by Sam; Sam would once again be in control of the reply-to.
6. Remove support for the deprecated GroupAccessRequestNotification from Thurloe
7. [this PR] Delete the deprecated GroupAccessRequestNotification from workbench-libs

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PR checklist

• For each library you've modified here, decide whether it requires a major, minor, or no version bump. (Click here for guidance)

If you're doing a major or minor version bump to any libraries:

• Bump the version in project/Settings.scala createVersion()
• Update CHANGELOG.md for those libraries
• I promise I used @deprecated instead of deleting code where possible

In all cases:

• Replace the appropriate version hashes in README.md and the CHANGELOG.md for any libs you changed with TRAVIS-REPLACE-ME to auto-update the version string
• Get two thumbsworth of PR review
• Verify all tests go green (CI and coverage tests)
• Squash commits and merge to develop
• Delete branch after merge

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 24.44%. Comparing base (4292239) to head (b65f241).
Report is 1 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #1719      +/-   ##
===========================================
- Coverage    24.45%   24.44%   -0.01%     
===========================================
  Files          105      105              
  Lines         2748     2745       -3     
  Branches       252      252              
===========================================
- Hits           672      671       -1     
+ Misses        2076     2074       -2     

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