Update dependency go to v1.25.4

Author: renovate[bot]

go.mod

@@ -2,7 +2,7 @@ module github.com/upbound/function-approve
 
 go 1.24.0
 
-toolchain go1.24.5
+toolchain go1.25.4
 
 require (
 	github.com/alecthomas/kong v1.12.1