DOC: don't say .loc is "strictly label-based" if it isn't

[BrenBarn]

One pedantic little thing I keep noticing: the docs for .loc say repeatedly that it is "strictly label-based", but it also accepts an array of booleans. I think it's good for .loc to have accept booleans, but it's misleading and confusing for the docs to say (in bold, no less) that it accepts only labels found in the index, and then immediately contradict themselves by saying it also accepts arrays of booleans. Booleans aren't labels found in the index.

[jreback]

welcome a PR to update to better reflect your views.

the 'strict' is simply that it uses the LABEL and not an integer to represent a positional indicator. I think that is clear. But if you think you can improve, then by all means.