Output of .guess_schema with --reasons is unreadable

[fsaad]

The MML versions is much more useful

[fsaad]

@curlette Consider removing the %mml .guess_schema --reasons from the documentation; having a pretty-print of the schema as MML code with reasons is not that trivial to implement and debug. Moreover, the returned code is not actual code because # is not a comment in BQL/MML.

[curlette]

Removed from docs in b1053a0. Remains to be removed from code.