chore(deps): bump actions/checkout from 4 to 6 #122

Job	Run time
Client Conformance (elicitation-sep1034-client-defaults)	1m 14s
Client Conformance (tools_call)	1m 20s
Server Conformance	1m 35s
Client Conformance (sse-retry)	1m 16s
Client Conformance (initialize)	1m 14s
Auth Conformance (auth/metadata-default)	1m 16s
Auth Conformance (auth/scope-from-www-authenticate)	1m 22s
Auth Conformance (auth/scope-step-up)	1m 18s
Auth Conformance (auth/metadata-var3)	1m 28s
Auth Conformance (auth/metadata-var2)	1m 13s
Auth Conformance (auth/token-endpoint-auth-post)	1m 19s
Auth Conformance (auth/scope-retry-limit)	1m 22s
Auth Conformance (auth/basic-cimd)	1m 22s
Auth Conformance (auth/metadata-var1)	1m 14s
Auth Conformance (auth/pre-registration)	1m 12s
Auth Conformance (auth/scope-omitted-when-undefined)	1m 17s
Auth Conformance (auth/token-endpoint-auth-none)	1m 16s
Auth Conformance (auth/token-endpoint-auth-basic)	1m 13s
Auth Conformance (auth/scope-from-scopes-supported)	1m 16s
	24m 47s

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