build: fix bash->sh function declaration

build/clean_go_build_cache.sh

 #!/bin/sh
 
-function version_gt() { test "$(printf '%s\n' "$@" | sort -V | head -n 1)" != "$1"; }
+version_gt() {
+  test "$(printf '%s\n' "$@" | sort -V | head -n 1)" != "$1"
+}
 
 golang_version=$(go version |cut -d' ' -f3 |sed 's/go//')