fix:updating pencil icon color to be accessible

[Maddiebusta]

jk i made this change in the wrong repository... ignore.

Jira: PRTL-4458

Overview:

Changing the color of the message draft icon to follow accessibility guidelines of being 3:1 contrast with the background.

Screenshots/GIFs:

Testing:

• [ ] Unit tests
• Manual tests:
  • [ ] Chrome
  • [ ] Safari
  • [ ] IE11

Roll Out:

• Before merging:
  • [ ] Updated docs
  • [ ] Bumped version in package.json
    • Breaking change?
      • If it is a beta component run npm version minor
      • If the component is not in beta run npm version major
    • New component or backward-compatible component feature change? Run npm version minor
    • Only changing documentation? All good. Skip this step.
  • After creating a new component, make sure to add it to the Components List in ComponentsView.jsx. To do so:
    • [ ] Add a screenshot of the component in docs/assets/img with the format <COMPONENT URL LINK>.png
• After merging:
  • [ ] Deployed updated docs (make deploy-docs)
  • [ ] Posted in #eng if I made a breaking change to a beta component