[CMSP-942] Adjust PHP EoS language in primary PHP Doc

[pwtyler]

Summary

PHP On Pantheon - Adjust language around unsupported versions of PHP
Related: #8896

Release:

• When ready

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Post Launch

Do not remove - To be completed by the docs team upon merge:

• Redirect /old-path/ => /new-path/ (if applicable)
• Include/exclude pages ^ respectively within docs search service provider (if applicable)
• For Heroes - add a props post to the discussion board.
• Remove from the project board

[pantheon-decoupled]

⚡ Deployed with Pantheon Decoupled

This build was successfully deployed with Pantheon. You can track the build logs here.

👀 Preview: https://pr-8898-documentation.appa.pantheon.site
🛠️ Manage in Pantheon: https://dashboard.pantheon.io/site/2b30153f-e8b1-4427-b076-6109e704ba5d/overview

[pwtyler]

Combining after all, see #8896