DOC-2419: TinyMCE 7.1.2 release notes and changelog.

[kemister85]

Ticket: DOC-2419

Site: Staging branch Site: Changelog

Changes:

• TinyMCE 7.1.2 release notes and changelog updates.

Pre-checks:

• [x] Branch prefixed with feature/<version>/, hotfix/<version>/, staging/<version>/, or release/<version>/
• [x] modules/ROOT/nav.adoc has been updated (if applicable)
• [x] Files has been included where required (if applicable)
• [x] Files removed have been deleted, not just excluded from the build (if applicable)
• [x] Files added for New product features, and included a release note entry.

Review:

• [x] Documentation Team Lead has reviewed