update fly to go 1.25 as well ...

Author: Bios-Marcel

fly.Dockerfile

@@ -4,7 +4,7 @@
 # We explicitly use a certain major version of go, to make sure we don't build
 # with a newer verison than we are using for CI tests, as we don't directly
 # test the produced binary but from source code directly.
-FROM docker.io/golang:1.23.3 AS builder
+FROM docker.io/golang:1.25.5 AS builder
 
 WORKDIR /app