docs: fix stale links and grammar, remove obsolete doc files

[armando-navarro]

Description

Sweeps a set of small documentation defects: stale links, one incorrect reference link, a wording fix, grammar, and two obsolete files.

• Point the two angular.io links (docs/compat.md, docs/compat/auth/router-guards.md) at angular.dev.
• Fix the App Check "Getting Started" link to the reCAPTCHA v3 provider page, matching the ReCaptchaV3Provider sample.
• docs/zones.md: correct the "Warn" logging-level bullet from "are called" to "are logged".
• Fix "Provide a" to "Provide an" in the Auth, Analytics, and App Check guides.
• Delete docs/firebase.json (a dead Firebase Hosting config) and docs/install-angular-cli-windows10.md (an obsolete, orphaned CLI install guide that recommends a deprecated tool).

Documentation only, no source or API changes.

Checklist

• Issue number for this PR: docs: stale links, a wrong reference link, and obsolete files in several guides #3733
• Docs included?: yes (documentation-only change)
• Test units included?: no (documentation-only change)
• In a clean directory, yarn install, yarn test run successfully?: not applicable, no code changed

Fixes #3733

[tyler-reitz]

All correct. The App Check link change in particular: the sample uses ReCaptchaV3Provider, which corresponds to the recaptcha-provider page rather than recaptcha-enterprise-provider, so the link now matches the code beside it.

Both deletions are justified. docs/firebase.json is a dead hosting config, and the Windows CLI guide points at windows-build-tools, which is archived — leaving it in place is worse than having no page at all.

Merge-order note: this and #3732 both touch docs/app-check.md and docs/auth.md with adjacent hunks. No overlap in substance, but whichever lands second should be rebased and re-skimmed rather than merged on a stale green.

[armando-navarro]

Thanks Tyler. The ReCaptchaV3Provider point is the one I was least sure about when I wrote it, so it is good to have it confirmed against the sample beside it.