Update Spotless + ktlint to latest versions

[kevinmost]

IMPORTANT: All PRs must be linked to an issue (except for extremely trivial and straightforward changes).

Description
Updates Spotless and ktlint, and re-runs ktlint.

ktlint had a bug that results in a cryptic error when attempting to use trailing commas (a valid Kotlin 1.4 feature). Updated ktlint to the latest version. Updated Spotless as well, and ran spotlessApply to apply the updated ktlint rules.

Type
Choose one: Code health

Checklist

• I have read and acknowledged the Code of conduct
• I have read How to Contribute
• I have read the Developer's guide
• I have signed the Google Individual CLA, or I am covered by my company's Corporate CLA
• I have discussed my proposed solution with code owners in the linked issue(s) and we have agreed upon the general approach
• I have run ./gradlew spotlessApply and ./gradlew spotlessCheck to check my code follows the style guide of this project
• I have run ./gradlew check and ./gradlew connectedCheck to test my changes locally
• I have built and run the reference app(s) to verify my change fixes the issue and/or does not break the reference app(s)

[jingtang10]

thanks so much for this!