updatecli: use shared policy apm-json-specs

[v1v]

Waiting for the package apm-json-specs to be available

This is sitting on the top of https://github.com/elastic/apm-agent-php/pull/1185

Tests

https://github.com/elastic/apm-agent-php/actions/runs/9805325194 created:

• https://github.com/elastic/apm-agent-php/pull/1187 vs https://github.com/elastic/apm-agent-php/pull/1189
• https://github.com/elastic/apm-agent-php/pull/1186 vs https://github.com/elastic/apm-agent-php/pull/1190