Revert "Part3: MDEV-18156 Assertion `0' failed or `btr_validate_index(index, 0, false)' in row_upd_sec_index_entry or error code 126: Index is corrupted upon DELETE with PAD_CHAR_TO_FULL_LENGTH"

This reverts commit 5a9e2b77 in 10.5,
so it produces an error on "bad" generated columns.

Note, 10.2, 10.3, 10.4 produce only warnings, for backward compatibility.