Update documentation for tls client auth eku removal

[mcpherrinm]

TLS Client Auth has been disabled in the default profile, so update docs

[Copilot]

Pull request overview

Updates Let’s Encrypt documentation to reflect the February 11, 2026 removal of the TLS Client Authentication EKU from the default certificate profile, and to clarify the remaining temporary tlsclient option.

Changes:

• Update lastmod dates to 2026-02-11 on affected English docs.
• Revise the “Removal of TLS Client Authentication EKU” entry to reflect that the removal has already occurred and point users to the temporary tlsclient profile.
• Update the tlsclient profile documentation to describe its EKU behavior and end-of-life date.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

File	Description
content/en/upcoming-features.md	Updates the EKU removal blurb and lastmod, but the item now reads as completed while still listed under “Upcoming Features”.
content/en/docs/profiles.md	Updates lastmod and rewrites the tlsclient section, but leaves the classic profile table/footnote indicating TLS Client Auth EKU is still present.

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