Remove unnecessary mocks

[eps1lon]

This mock isn't needed and, from my experience, mocking React never made for robust tests.

Closes NEXT-3285

[ijjk]

Stats from current PR

Default Build

General

	vercel/next.js canary	vercel/next.js sebbie/test-mock	Change
buildDuration	19.3s	17.5s	N/A
buildDurationCached	10.1s	9.2s	N/A
nodeModulesSize	360 MB	360 MB	✓
nextStartRea..uration (ms)	453ms	469ms	N/A

Client Bundles (main, webpack)

	vercel/next.js canary	vercel/next.js sebbie/test-mock	Change
1103-HASH.js gzip	31.9 kB	31.9 kB	N/A
1a9f679d-HASH.js gzip	53.5 kB	53.5 kB	N/A
335-HASH.js gzip	5.05 kB	5.05 kB	✓
7953.HASH.js gzip	169 B	169 B	✓
framework-HASH.js gzip	45.2 kB	45.2 kB	✓
main-app-HASH.js gzip	231 B	229 B	N/A
main-HASH.js gzip	31.6 kB	31.6 kB	N/A
webpack-HASH.js gzip	1.65 kB	1.65 kB	N/A
Overall change	50.4 kB	50.4 kB	✓

Legacy Client Bundles (polyfills)

	vercel/next.js canary	vercel/next.js sebbie/test-mock	Change
polyfills-HASH.js gzip	31 kB	31 kB	✓
Overall change	31 kB	31 kB	✓

Client Pages

	vercel/next.js canary	vercel/next.js sebbie/test-mock	Change
_app-HASH.js gzip	192 B	193 B	N/A
_error-HASH.js gzip	192 B	193 B	N/A
amp-HASH.js gzip	507 B	511 B	N/A
css-HASH.js gzip	341 B	343 B	N/A
dynamic-HASH.js gzip	2.52 kB	2.52 kB	✓
edge-ssr-HASH.js gzip	266 B	265 B	N/A
head-HASH.js gzip	362 B	365 B	N/A
hooks-HASH.js gzip	392 B	392 B	✓
image-HASH.js gzip	4.27 kB	4.27 kB	✓
index-HASH.js gzip	268 B	268 B	✓
link-HASH.js gzip	2.69 kB	2.7 kB	N/A
routerDirect..HASH.js gzip	329 B	328 B	N/A
script-HASH.js gzip	397 B	397 B	✓
withRouter-HASH.js gzip	324 B	324 B	✓
1afbb74e6ecf..834.css gzip	106 B	106 B	✓
Overall change	8.27 kB	8.27 kB	✓

Client Build Manifests

	vercel/next.js canary	vercel/next.js sebbie/test-mock	Change
_buildManifest.js gzip	483 B	484 B	N/A
Overall change	0 B	0 B	✓

Rendered Page Sizes

	vercel/next.js canary	vercel/next.js sebbie/test-mock	Change
index.html gzip	527 B	526 B	N/A
link.html gzip	540 B	538 B	N/A
withRouter.html gzip	522 B	521 B	N/A
Overall change	0 B	0 B	✓

Edge SSR bundle Size

	vercel/next.js canary	vercel/next.js sebbie/test-mock	Change
edge-ssr.js gzip	94.7 kB	94.7 kB	N/A
page.js gzip	182 kB	182 kB	N/A
Overall change	0 B	0 B	✓

Middleware size

	vercel/next.js canary	vercel/next.js sebbie/test-mock	Change
middleware-b..fest.js gzip	624 B	623 B	N/A
middleware-r..fest.js gzip	156 B	156 B	✓
middleware.js gzip	25.7 kB	25.7 kB	N/A
edge-runtime..pack.js gzip	839 B	839 B	✓
Overall change	995 B	995 B	✓

Next Runtimes

	vercel/next.js canary	vercel/next.js sebbie/test-mock	Change
app-page-exp...dev.js gzip	171 kB	171 kB	✓
app-page-exp..prod.js gzip	98.7 kB	98.7 kB	✓
app-page-tur..prod.js gzip	100 kB	100 kB	✓
app-page-tur..prod.js gzip	94.5 kB	94.5 kB	✓
app-page.run...dev.js gzip	157 kB	157 kB	✓
app-page.run..prod.js gzip	93.2 kB	93.2 kB	✓
app-route-ex...dev.js gzip	21.5 kB	21.5 kB	✓
app-route-ex..prod.js gzip	15.2 kB	15.2 kB	✓
app-route-tu..prod.js gzip	15.2 kB	15.2 kB	✓
app-route-tu..prod.js gzip	15 kB	15 kB	✓
app-route.ru...dev.js gzip	21.3 kB	21.3 kB	✓
app-route.ru..prod.js gzip	15 kB	15 kB	✓
pages-api-tu..prod.js gzip	9.55 kB	9.55 kB	✓
pages-api.ru...dev.js gzip	9.82 kB	9.82 kB	✓
pages-api.ru..prod.js gzip	9.55 kB	9.55 kB	✓
pages-turbo...prod.js gzip	21.5 kB	21.5 kB	✓
pages.runtim...dev.js gzip	22.1 kB	22.1 kB	✓
pages.runtim..prod.js gzip	21.5 kB	21.5 kB	✓
server.runti..prod.js gzip	51.6 kB	51.6 kB	✓
Overall change	963 kB	963 kB	✓

build cache

	vercel/next.js canary	vercel/next.js sebbie/test-mock	Change
0.pack gzip	1.62 MB	1.62 MB	N/A
index.pack gzip	114 kB	114 kB	N/A
Overall change	0 B	0 B	✓

Diff details

Diff for edge-ssr.js

Diff too large to display

Commit: 2202e54