[Security] Fixing PHP example for limiting login attempts with rate limiter

[MirakuSan]

After struggling with the rate limiter on my app.
I think the PHP example for « limiting login attempts » with a rate limiter has a bad copy/paste for the third option to pass to the container to register the DefaultLoginRateLimiter::class.

Using new Reference('kernel.secret') , I had an error telling me No services 'kernel.secret' found

Here is what I used and worked for me and so it is my proposal 🙏

[xabbuh]

Good catch @MirakuSan 👍 Can you please update the XML example as well (i.e. change line 1656 to <srv:argument type="string">%kernel.secret%</srv:argument>)?

[MirakuSan]

yeap @xabbuh, I'll do this asap! 🙏

Edit: Done ✅

[javiereguiluz]

Good catch Damien! Thanks and congrats on your first Symfony Docs contribution 🎉

[MirakuSan]

Thanks @javiereguiluz but this is not my first contribution 😄

[javiereguiluz]

Sorry ... but GitHub displayed the "New contributor" label on your contribution 😐