docs: Incremental cache is not used for cache-control: no-cache requests

[icyJoseph]

Closes: #80346

• next.js/packages/next/src/server/lib/patch-fetch.ts

  Lines 807 to 812 in 2f63e47

  	if (entry) {
  	await handleUnlock()
  	} else {
  	// in dev, incremental cache response will be null in case the browser adds `cache-control: no-cache` in the request headers
  	cacheReasonOverride = 'cache-control: no-cache (hard refresh)'
  	}

• next.js/packages/next/src/server/lib/incremental-cache/index.ts

  Lines 417 to 426 in 2f63e47

  	// we don't leverage the prerender cache in dev mode
  	// so that getStaticProps is always called for easier debugging
  	if (
  	this.disableForTestmode ||
  	(this.dev &&
  	(ctx.kind !== IncrementalCacheKind.FETCH ||
  	this.requestHeaders['cache-control'] === 'no-cache'))
  	) {
  	return null
  	}