remove reference to library for tokenization in example code

[pazzo83]

Removing reference to the TextAnalysis version of tokenize in example code as it (for some reason) introduces the need to pass a language argument which is unused.

[ablaom]

This is great, thanks, @pazzo83 . However, there are also docstrings to fix, e.g. here:

MLJText.jl/src/docstring_helpers.jl

Line 53 in d04938d

julia> tokenized_docs = TextAnalysis.tokenize.(docs)