fix: add missing SCHEMA @tag location

[dariuszkuc]

Starting with Federation v2.3 @tag is applicable on SCHEMA as well.

[github-actions]

Apollo Federation Subgraph Compatibility Results

Federation 1 Support	Federation 2 Support
_service 🟢 @key (single) 🟢 @key (multi) 🟢 @key (composite) 🟢 repeatable @key 🟢 @requires 🟢 @provides 🟢 federated tracing 🟢	@link 🟢 @shareable 🟢 @tag 🟢 @override 🟢 @inaccessible 🟢 @composeDirective 🟢 @interfaceObject 🟢

Learn more:

• Apollo Federation Subgraph Specification
• Compatibility Tests

[dariuszkuc]

Updated to minor as while it is a fix it is also a new feature (adding new SCHEMA location)