fix: only create one notice when siteToken cant activate

[justlevine]

What

Fixes a React bug where multiple setting notices were created when the site token mutation cannot be actived.

Why

How

We now only create the notice when the provider changes from enabled to disabled.

Testing Instructions

1. Set Block Unauthorized Domains to true.
2. Enable the Site Token provider.
3. Set Block Unauthorized Domains to false.
4. Inspect DOM and React Component tree.

Additional Info

Checklist:

• [x] My code is tested to the best of my abilities.
• [x] My code follows the WordPress Coding Standards.
• [x] My code has proper inline documentation.
• [x] I have added unit tests to verify the code works as intended.
• [x] I included the relevant changes in CHANGELOG.md

[coveralls]

Coverage: 83.741%. Remained the same when pulling aadd35f6b9a289a650f79d0d8471cf9b9bf8a326 on justlevine:fix/site-token-activation-failure-notice into d8d1971fcbf53ce7db9dd060eff283557135a53b on AxeWP:develop.