CLN: remove unsupported sparse code from io.pytables
AFAICT this is a legacy of SparseDataFrame
I think we're good removing these. There's a brief conversation in https://github.com/pandas-dev/pandas/pull/28425/files/b6fb1aabc19515672e840c7d0b30fafee1b88844#diff-1b15d1477da3a0548d2dd72a5d023d00 (where I removed SparseDataFrame & Series). IIRC, I had some hacks to try supporting it, but things looked generally broken for `DataFrame[sparse]`. I think I just forgot to remove this methods. rebased+green thanks