LU-16518 obdclass: fix unused-but-set-variable warnings

LU-16518 obdclass: fix unused-but-set-variable warnings

Remove swab variable in class_config_yaml_output()
that is not being used.

Test-Parameters: trivial
Signed-off-by: Timothy Day <timday@amazon.com>
Change-Id: I0db780c98fe34cef91988fc3f8c2ccac9481de2c
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/58179
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Max Wang <wamax@amazon.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: Oleg Drokin <green@whamcloud.com>
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>