lang/php86: Update version 8.6.0alpha1=>8.6.0alpha2

Please DO NOT use this version in production, it is an early test version.

For upgrade notes please visit:
https://github.com/php/php-src/blob/php-8.6.0alpha2/UPGRADING

Changelog: https://github.com/php/php-src/blob/php-8.6.0alpha2/NEWS