--steam-runtime option is not used in cofigure.sh script, but the help message mentions that option.

./configure.sh --help
::   Steam Runtime
::     Proton builds that are to be installed & run under the steam client must be built with
::     the Steam Runtime SDK to ensure compatibility.  See README.md for more information.
:: 
...
::     --steam-runtime=soldier  Name of the steam runtime release to build for (soldier, scout).
...

Steps to reproduce

Issue the following command.

./configure.sh --steam-runtime=sniper

Actual Result

!! Unrecognized option --steam-runtime
!! Usage: ../configure.sh { --no-proton-sdk | --proton-sdk-image=<image> --steam-runtime=<name> }
...

Expected Result

Should we delete the help text of that option?