[TextInput] Certain props should be optional

[tanner-ricks]

[Short description explaining the high-level reason for the pull request]

Changes

• TextInput.tsx: Updated the property typing to fix an issue which caused properties that should be optional, to be considered mandatory instead.

How to test this PR

1. View and verify the the deploy preview
2. Pull 308-ts-error-fix
3. Run yarn lint against the branch
4. Verify that TextInput.tsx has no errors
5. Run yarn test against the branch and verify that everything passes
6. Build the package
7. Update the package.json in sbl-frontend to include "design-system-react": "file:./<path-to-package.tgz>/package.tgz"
8. Run yarn install
9. Pull 986-default-max-length in sbl-frontend
10. Verify that TextInput.tsx in sbl-frontend has no errors

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[meissadia]

LGTM 👍🏾