(table-hooks): Finish `defgroup' description with period.

(table-hooks): Finish `defgroup' description with period.
(table-insert, table-shorten-cell, table--generate-source-scan-lines,
table-delete-row, *table--cell-delete-char, table--spacify-frame,
table--horizontally-shift-above-and-below, table--cell-insert-char,
table--cell-blank-str, table--fill-region-strictly): "?\ " -> "?\s".