Clean up code/testing artifacts from #7014

[keanulee]

Didn't realize that last PR would be merged so fast! Here's some things I wanted to clean up that I didn't get a chance to squeeze in #7014 (no functionality change).

[timneutkens]

💯 Awesome!

[github-actions]

Stats from current PR

Click to expand stats

	zeit/next.js canary	keanulee/next.js modern-pr-cleanup	Change
Build Duration	14.1s	14.1s	⚠️ +24ms
node_modules Size	39.6 MB	39.6 MB	-330 B
Total Bundle (main, webpack, commons) Size	209 kB	209 kB	✓
Total Bundle (main, webpack, commons) gzip Size	68.5 kB	68.5 kB	✓
Client _app Size	2.6 kB	2.6 kB	✓
Client _app gzip Size	1.07 kB	1.07 kB	✓
Client _error Size	8.14 kB	8.14 kB	✓
Client _error gzip Size	3.1 kB	3.1 kB	✓
Client pages/index Size	288 B	288 B	✓
Client pages/index gzip Size	222 B	222 B	✓
Client pages/link Size	4.78 kB	4.78 kB	✓
Client pages/link gzip Size	2.09 kB	2.09 kB	✓
Client pages/routerDirect Size	411 B	411 B	✓
Client pages/routerDirect gzip Size	296 B	296 B	✓
Client pages/withRouter Size	393 B	393 B	✓
Client pages/withRouter gzip Size	280 B	280 B	✓
Client main Size	23.3 kB	23.3 kB	✓
Client main gzip Size	7.63 kB	7.63 kB	✓
Client commons Size	183 kB	183 kB	✓
Client commons gzip Size	59.5 kB	59.5 kB	✓
Client webpack Size	1.49 kB	1.49 kB	✓
Client webpack gzip Size	769 B	769 B	✓
Base Rendered Size	1.34 kB	1.34 kB	✓
Build Dir Size	803 kB	803 kB	✓

Click to expand serverless stats

	zeit/next.js canary	keanulee/next.js modern-pr-cleanup	Change
Build Duration	15.9s	15.4s	-575ms
node_modules Size	39.6 MB	39.6 MB	-330 B
Total Bundle (main, webpack, commons) Size	209 kB	209 kB	✓
Total Bundle (main, webpack, commons) gzip Size	68.5 kB	68.5 kB	✓
Client _app Size	2.6 kB	2.6 kB	✓
Client _app gzip Size	1.07 kB	1.07 kB	✓
Client _error Size	8.14 kB	8.14 kB	✓
Client _error gzip Size	3.1 kB	3.1 kB	✓
Client pages/index Size	288 B	288 B	✓
Client pages/index gzip Size	222 B	222 B	✓
Client pages/link Size	4.78 kB	4.78 kB	✓
Client pages/link gzip Size	2.09 kB	2.09 kB	✓
Client pages/routerDirect Size	411 B	411 B	✓
Client pages/routerDirect gzip Size	296 B	296 B	✓
Client pages/withRouter Size	393 B	393 B	✓
Client pages/withRouter gzip Size	280 B	280 B	✓
Client main Size	23.3 kB	23.3 kB	✓
Client main gzip Size	7.63 kB	7.63 kB	✓
Client commons Size	183 kB	183 kB	✓
Client commons gzip Size	59.5 kB	59.5 kB	✓
Client webpack Size	1.49 kB	1.49 kB	✓
Client webpack gzip Size	769 B	769 B	✓
Serverless pages/link Size	343 kB	343 kB	✓
Serverless pages/link gzip Size	88.8 kB	88.8 kB	✓
Serverless pages/index Size	334 kB	334 kB	✓
Serverless pages/index gzip Size	86.4 kB	86.4 kB	✓
Serverless pages/_error Size	334 kB	334 kB	✓
Serverless pages/_error gzip Size	86.2 kB	86.2 kB	✓
Serverless pages/routerDirect Size	334 kB	334 kB	✓
Serverless pages/routerDirect gzip Size	86.5 kB	86.5 kB	✓
Serverless pages/withRouter Size	334 kB	334 kB	✓
Serverless pages/withRouter gzip Size	86.6 kB	86.6 kB	✓
Build Dir Size	2.37 MB	2.37 MB	✓