Update AGP reference in the Core WG charter to SLIM

[natalisucks]

The Core WG charter still lists Agent Gateway Protocol (AGP), however, this has been renamed to Secure Low-Latency Interactive Messaging (SLIM) some time ago and needs to be updated. See the sub-project here: https://github.com/agntcy/slim

Link to charter: https://github.com/agntcy/governance/blob/main/working-groups/core/CHARTER.md

I would also recommend in that same update that certain core components, if contained as a singular sub-project, also have the repositories linked to in the charter.

[muscariello]

Core WG needs to be updated also because we are deprecating ACP in favor of A2A. I will propose an update and ask TSC approval for that.

[stibrewa]

Great to see "good First issue "