LU-16523 lprocfs: adjust the format of rename_stats

LU-16523 lprocfs: adjust the format of rename_stats

Adjust the format of rename_stats to a more human-friendly YAML.

Fixes: bedb797c5d ("LU-16110 lprocfs: make job_stats and rename_stats valid YAML")
Signed-off-by: Lei Feng <flei@whamcloud.com>
Test-Parameters: trivial
Change-Id: I20e6d07c974e907bb2e30412dd1899f845de2021
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/49869
Tested-by: Maloo <maloo@whamcloud.com>
Tested-by: jenkins <devops@whamcloud.com>
Reviewed-by: Lai Siyao <lai.siyao@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>