Update FAQ to reflect the default value of src

[dhruvmanila]

Update to FAQ.md at https://github.com/astral-sh/ruff/blob/main/docs/faq.md is merited as a result of this change I think.

Specifically, the following bullet can be removed:

Depending on your project structure, Ruff and isort can differ in their detection of first-party code. (This is often solved by modifying the src property, e.g., to src = ["src"], if your code is nested in a src directory.)

Originally posted by @NasaGeek in #12848 (comment)

[dhruvmanila]

I think we should instead highlight the fact that this was changed in 0.6 instead of removing the bullet point.

[PalAditya]

Hi @dhruvmanila - I love Ruff and wanted to contribute to it for some time, so just made a PR for this: #13145 . I didn't see anything in the contributing guidelines about prior assignment, but please let me know if it needs changes/I should have completed some pre-requisite first if you get a chance to review this.