tools: fix argv bug in find-inactive-tsc.mjs

The argument supplied is expected to be text, not numeric.

This wasn't causing issues with the automated job because it does not
send an argument. It uses the default.

PR-URL: nodejs#41394
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Richard Lau <rlau@redhat.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Anto Aravinth <anto.aravinth.cse@gmail.com>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>
Reviewed-By: Zijian Liu <lxxyxzj@gmail.com>
Reviewed-By: Anatoli Papirovski <apapirovski@mac.com>

tools/find-inactive-tsc.mjs

@@ -13,7 +13,7 @@ import fs from 'node:fs';
 import path from 'node:path';
 import readline from 'node:readline';
 
-const SINCE = +process.argv[2] || '3 months ago';
+const SINCE = process.argv[2] || '3 months ago';
 
 async function runGitCommand(cmd, options = {}) {
   const childProcess = cp.spawn('/bin/sh', ['-c', cmd], {