fix(ci/benchmark): Unbreak "Push reports to data branch" step

The `report_subfolder` variable was being populated with two identical lines, because there will be two untracked files in the folder, resulting in the same dirname.
This caused later commands using that variable to fail. Fix is to `sort -u` before storing the value to `report_subfolder`.

.github/workflows/autogpts-benchmark.yml

@@ -75,7 +75,8 @@ jobs:
           report_subfolder=$(find ${{ env.REPORTS_FOLDER }} -type f -name 'report.json' \
             | xargs -I {} dirname {} \
             | xargs -I {} git ls-files --others --exclude-standard {} \
-            | xargs -I {} dirname {})
+            | xargs -I {} dirname {} \
+            | sort -u)
           json_report_file="$report_subfolder/report.json"
 
           # Convert JSON report to Markdown