DOC: #7927. Remove deprecated note for memmap relevant for Python <2.5

[tom-bird]

No description provided.

[juliantaylor]

thanks
There should still be a short note that files cannot be larger than 2GiB on 32 bit systems which is independent of python version.

(you can add [ci skip] to the commit message to skip the unnecessary travis check on documentation updates)

[tom-bird]

Gotcha, thanks

[charris]

Thanks @theultimatecrouton .