chore: remove unused goreleaser checksum script

.goreleaser.checksum.sh

@@ -1,12 +0,0 @@
-#!/bin/bash
-
-set -e
-
-if [ -z "$1" ]; then
-  echo "usage: $0 <path>"
-  exit 1
-fi
-
-SUM=$(shasum -a 256 "$1" | cut -d' ' -f1)
-BASENAME=$(basename "$1")
-echo -n "${SUM}  ${BASENAME}" > "$1".sha256