gh-137952: update `csv.Sniffer().has_header()` docs to describe the actual off-by-onish behavior#137953

maurycy wants to merge 2 commits intopython:mainpython/cpython:mainfrom

maurycy:csv-sniffer-has_headers-off-by-onemaurycy/cpython:csv-sniffer-has_headers-off-by-oneCopy head branch name to clipboard