Remove mention of the Next.js site repo from docs

[lfades]

Fixes #19503

[ijjk]

Stats from current PR

Default Server Mode (Decrease detected ✓)

General

	vercel/next.js canary	lfades/next.js remove-mentions-of-the-next-js-site-repo-ch15889	Change
buildDuration	8.7s	8.7s	-44ms
nodeModulesSize	84.9 MB	84.9 MB	✓

Page Load Tests Overall decrease ⚠️

	vercel/next.js canary	lfades/next.js remove-mentions-of-the-next-js-site-repo-ch15889	Change
/ failed reqs	0	0	✓
/ total time (seconds)	1.963	2.021	⚠️ +0.06
/ avg req/sec	1273.74	1237.02	⚠️ -36.72
/error-in-render failed reqs	0	0	✓
/error-in-render total time (seconds)	1.151	1.157	⚠️ +0.01
/error-in-render avg req/sec	2172.27	2160.71	⚠️ -11.56

Client Bundles (main, webpack, commons)

	vercel/next.js canary	lfades/next.js remove-mentions-of-the-next-js-site-repo-ch15889	Change
677f882d2ed8..8b81.js gzip	12.8 kB	12.8 kB	✓
framework.HASH.js gzip	39 kB	39 kB	✓
main-fbd7082..8b7a.js gzip	6.54 kB	6.54 kB	✓
webpack-e067..f178.js gzip	751 B	751 B	✓
Overall change	59 kB	59 kB	✓

Legacy Client Bundles (polyfills)

	vercel/next.js canary	lfades/next.js remove-mentions-of-the-next-js-site-repo-ch15889	Change
polyfills-4b..e242.js gzip	31 kB	31 kB	✓
Overall change	31 kB	31 kB	✓

Client Pages

	vercel/next.js canary	lfades/next.js remove-mentions-of-the-next-js-site-repo-ch15889	Change
_app-3b0cf13..85f8.js gzip	1.28 kB	1.28 kB	✓
_error-6f635..c393.js gzip	3.44 kB	3.44 kB	✓
hooks-d4ffc3..9e0f.js gzip	887 B	887 B	✓
index-17468f..5d83.js gzip	227 B	227 B	✓
link-b618194..5477.js gzip	1.61 kB	1.61 kB	✓
routerDirect..924c.js gzip	284 B	284 B	✓
withRouter-7..c13d.js gzip	284 B	284 B	✓
Overall change	8.01 kB	8.01 kB	✓

Client Build Manifests

	vercel/next.js canary	lfades/next.js remove-mentions-of-the-next-js-site-repo-ch15889	Change
_buildManifest.js gzip	321 B	321 B	✓
Overall change	321 B	321 B	✓

Rendered Page Sizes

	vercel/next.js canary	lfades/next.js remove-mentions-of-the-next-js-site-repo-ch15889	Change
index.html gzip	614 B	614 B	✓
link.html gzip	621 B	621 B	✓
withRouter.html gzip	608 B	608 B	✓
Overall change	1.84 kB	1.84 kB	✓

---

Serverless Mode

General

	vercel/next.js canary	lfades/next.js remove-mentions-of-the-next-js-site-repo-ch15889	Change
buildDuration	10.3s	9.9s	-374ms
nodeModulesSize	84.9 MB	84.9 MB	✓

Client Bundles (main, webpack, commons)

	vercel/next.js canary	lfades/next.js remove-mentions-of-the-next-js-site-repo-ch15889	Change
677f882d2ed8..8b81.js gzip	12.8 kB	12.8 kB	✓
framework.HASH.js gzip	39 kB	39 kB	✓
main-fbd7082..8b7a.js gzip	6.54 kB	6.54 kB	✓
webpack-e067..f178.js gzip	751 B	751 B	✓
Overall change	59 kB	59 kB	✓

Legacy Client Bundles (polyfills)

	vercel/next.js canary	lfades/next.js remove-mentions-of-the-next-js-site-repo-ch15889	Change
polyfills-4b..e242.js gzip	31 kB	31 kB	✓
Overall change	31 kB	31 kB	✓

Client Pages

	vercel/next.js canary	lfades/next.js remove-mentions-of-the-next-js-site-repo-ch15889	Change
_app-3b0cf13..85f8.js gzip	1.28 kB	1.28 kB	✓
_error-6f635..c393.js gzip	3.44 kB	3.44 kB	✓
hooks-d4ffc3..9e0f.js gzip	887 B	887 B	✓
index-17468f..5d83.js gzip	227 B	227 B	✓
link-b618194..5477.js gzip	1.61 kB	1.61 kB	✓
routerDirect..924c.js gzip	284 B	284 B	✓
withRouter-7..c13d.js gzip	284 B	284 B	✓
Overall change	8.01 kB	8.01 kB	✓

Client Build Manifests

	vercel/next.js canary	lfades/next.js remove-mentions-of-the-next-js-site-repo-ch15889	Change
_buildManifest.js gzip	321 B	321 B	✓
Overall change	321 B	321 B	✓

Serverless bundles

	vercel/next.js canary	lfades/next.js remove-mentions-of-the-next-js-site-repo-ch15889	Change
_error.js	915 kB	915 kB	✓
404.html	2.67 kB	2.67 kB	✓
hooks.html	1.92 kB	1.92 kB	✓
index.js	915 kB	915 kB	✓
link.js	973 kB	973 kB	✓
routerDirect.js	966 kB	966 kB	✓
withRouter.js	966 kB	966 kB	✓
Overall change	4.74 MB	4.74 MB	✓

Commit: bc7bb51