We recently switched to more explicit GPL license names in line
with the SPDX change and GNU Foundation recommendations:
https://www.gnu.org/licenses/identify-licenses-clearly.html
This followed up older change to use the recommended SPDX ID
18a5e8c36b
but using the `-only` variant for these deprecated licenses too
makes it harder to check for them automatically.
Let’s switch to the appropriate SPDX ID again.
9d5bd8b835