check-by-name: Remove legacy script

fetch-tool.sh was decommissioned in
https://github.com/NixOS/nixpkgs/pull/281374, see the removed comment
for why it can only be removed now

pkgs/test/nixpkgs-check-by-name/scripts/fetch-tool.sh

@@ -1,19 +0,0 @@
-#!/usr/bin/env bash
-# Legacy script to make CI work for the PR that replaces this
-# Needed due to `.github/workflows/check-by-name.yml` using `pull_request_target`,
-# which uses the workflow from the base branch, which still uses this script.
-# This file can be removed after the PR replacing it is merged.
-
-trace() { echo >&2 "$@"; }
-
-if (( $# < 2 )); then
-    trace "Usage: $0 BASE_BRANCH OUTPUT_PATH"
-    trace "BASE_BRANCH (unused): The base branch to use, e.g. master or release-23.11"
-    trace "OUTPUT_PATH: The output symlink path for the tool"
-    exit 1
-fi
-output=$2
-
-SCRIPT_DIR=$( cd -- "$( dirname -- "${BASH_SOURCE[0]}" )" &> /dev/null && pwd )
-
-"$SCRIPT_DIR"/fetch-pinned-tool.sh "$output"