stop triggering duplicate unit tests on PRs

[clairep94]

Issue:

Fixes #

• current setup makes it so that every time we open a PR, it triggers 2 runs of the unit test workflow
• this updates so that:
  • opening a PR to any branch triggers a single unit test run
  • updating a PR to any branch triggers a single unit test run
  • pushing to develop triggers a single unit test run
  • pushing to release triggers a single unit test run

Demo:

Before - 2 unit tests:

After - 1 unit test:

Changes:

I have verified that this pull request:

• has no linting errors (npm run lint)
• has no test errors (npm run test)
• has no typecheck errors (npm run typecheck)
• is from a uniquely-named feature branch and is up to date with the develop branch.
• is descriptively named and links to an issue number, i.e. Fixes #123
• meets the standards outlined in the accessibility guidelines