infra: update check-performance-regression.yml to have no extra folder

[romani]

https://github.com/checkstyle/checkstyle/actions/runs/8934444831/job/24541391465?pr=14779#step:6:9

0s
Run cd checkstyle
  cd checkstyle
  bash ./.ci/check-performance-regression.sh
  shell: /usr/bin/bash -e {0}
  env:
    JAVA_HOME: /opt/hostedtoolcache/Java_Temurin-Hotspot_jdk/11.0.22-7/x64
    JAVA_HOME_11_X64: /opt/hostedtoolcache/Java_Temurin-Hotspot_jdk/11.0.22-7/x64
bash: ./.ci/check-performance-regression.sh: No such file or directory

[romani]

https://github.com/checkstyle/checkstyle/actions/runs/8939370455/job/24555267920?pr=14851#step:6:339

not failing but:

Benchmark launching...
================ MOST RECENT COMMAND RESULT =================
Files to process must be specified, found 0.
===================== BENCHMARK SUMMARY ====================
Execution Time Baseline: 415.72 s
Average Execution Time: .26 s
============================================================
Execution Time Difference: -99.9300%
Difference is within the maximum allowed difference (-99.9300%      <= 10%).

we need to merge to unblock other PRs, and fix it in separte PR.

[nrmancuso]

#14852