chore(go-cache): remove stale local replace directive per AX-6

Removed local `replace dappco.re/go/io => ../go-io` — upstream module
now resolvable via proper registry (go-io migrated via #629). Replace
directive was leftover dev-mode bypass.

Closes tasks.lthn.sh/view.php?id=787

Co-authored-by: Codex <noreply@openai.com>

Author: Snider

go.mod

@@ -6,5 +6,3 @@ require (
 	dappco.re/go/core v0.8.0-alpha.1
 	dappco.re/go/io v0.4.1
 )
-
-replace dappco.re/go/io => ../go-io