tools: adjust script for use with 14.x

find-inactive-collaborators.mjs works fine with Node.js 16.x, but GitHub
Actions currently use 14.x by default. This PR makes a small adjustment
so that it works with 14.x. (14.x does not accept URL objects as
paramemters for the `cwd` option in `spawn()`.)

tools/find-inactive-collaborators.mjs

@@ -12,7 +12,8 @@ const SINCE = process.argv[2] || '6 months ago';
 
 async function runGitCommand(cmd, mapFn) {
   const childProcess = cp.spawn('/bin/sh', ['-c', cmd], {
-    cwd: new URL('..', import.meta.url),
+    // TODO: remove pathname after https://github.com/nodejs/node/pull/38862 is backported to v14.x.
+    cwd: new URL('..', import.meta.url).pathname,
     encoding: 'utf8',
     stdio: ['inherit', 'pipe', 'inherit'],
   });