Legend Compatibility Issue in `_legend.py` for `obj.ncols` (Matplotlib 3.6.0 Update)

[thekpaul]

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I'm no expert in any of this but I've tried the fix suggested in #557, seems to work in some test cases I've tried. Maybe just an overlooked detail?

(Apparently _ncol is outdated now as per Matplotlib API Docs, but I left line 82 as is in case anything else goes wrong)

[2sn]

would be good to include / merge.