Removed outdated note in oob swap documentation

[Telroshan]

Description

3 years ago, @1cg pushed this commit

allow hx-swap-oob to be at any level in returned content

Yet 3 years later, the hx-swap-oob documentation still states the following:

Out of band elements must be in the top level of the response, and not children of the top level elements.

which doesn't seem to be true anymore, given that the commit mentioned above introduced a test case for the nested elements scenario.

Btw, this also seems to make the multi-swap extension kinda obsolete now as its reason to exist as per its doc was:

Multi-swap can help in cases where OOB (Out of Band Swaps) is not enough for you. OOB requires HTML tags marked with hx-swap-oob attributes to be at the TOP level of HTML, which significantly limited its use. With OOB, it’s impossible to swap multiple elements arbitrarily placed and nested in the DOM tree.

Checklist

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  source changes)
• This is either a bugfix, a documentation update, or a new feature that has been explicitly
  approved via an issue
• I ran the test suite locally (npm run test) and verified that it succeeded