docs: Use correct name for Intelephense license file (#26986)

This PR updates the Intelephense section of the PHP docs to use the
correct name for the license file.

Intelephense uses British English:

<img width="1185" alt="Screenshot 2025-03-18 at 8 30 20 AM"
src="https://github.com/user-attachments/assets/a675e854-bedf-4f70-bf8f-90488d196242"
/>

Release Notes:

- N/A