perf/run_perf: adjust indentations for help message

Signed-off-by: Kamil Godzwon <kamilx.godzwon@intel.com>
Change-Id: I4b58d7881f2bcf88d48dd495535bf89693da37bc
Reviewed-on: https://review.spdk.io/gerrit/c/spdk/spdk/+/19935


Reviewed-by: Pawel Piatek <pawelx.piatek@intel.com>
Reviewed-by: Tomasz Zawadzki <tomasz.zawadzki@intel.com>
Reviewed-by: Karol Latecki <karol.latecki@intel.com>
Tested-by: SPDK CI Jenkins <sys_sgci@intel.com>
Reviewed-by: Konrad Sztyber <konrad.sztyber@intel.com>