[mdoc] Bq not terminated by Ta

Hi all,

I am sure Branden is gonna be happy because I found another questionable
behavior of groff's mdoc implementation. When using Bq in a columnated
list (aka a table), Bq encloses everything until end of input line in
square brackets, rather than just the stuff until next Ta (i.e. column
separator). No diagnostics are produced. mandoc does not exhibit this
behavior.

Example to reproduce:
  .Dd October 30, 2025
  .Dt EXAMPLE 1
  .Os
  .Sh DESCRIPTION
  .Bl -column [One] [Two] [Three]
  .It Bq One Ta Bq Two Ta Bq Three
  .El

Cheers,
onf