tools: ynl: avoid bare except

This 'except' was used without specifying the exception class according
to Ruff. Here, only the ValueError class is expected and handled.

This is linked to Ruff error E722 [1]:

  A bare except catches BaseException which includes KeyboardInterrupt,
  SystemExit, Exception, and others. Catching BaseException can make it
  hard to interrupt the program (e.g., with Ctrl-C) and can disguise
  other problems.

Link: https://docs.astral.sh/ruff/rules/bare-except/

 [1]
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Reviewed-by: Donald Hunter <donald.hunter@gmail.com>
Reviewed-by: Asbjørn Sloth Tønnesen <ast@fiberby.net>
Link: https://patch.msgid.link/20250909-net-next-ynl-ruff-v1-2-238c2bccdd99@kernel.org


Signed-off-by: Jakub Kicinski <kuba@kernel.org>