Check perf results is too sensitive - non-regression noise exceeds 2 sigma variation

The script uses the default value for max_sigma, which is 2. Consider passing a higher threshold to avoid false positives on regressions.

https://github.com/microsoft/ebpf-for-windows/blob/13cadc66cb5f59d94e13e345f49b116914da4d88/.github/workflows/upload-perf-results.yml#L105

https://github.com/microsoft/bpf_performance/blob/492e048521959aa0e679e8779d8cdf743da0a9a1/scripts/check_perf_results.sql#L24

Start with the workflow invocation at .github/workflows/upload-perf-results.yml#L105 and the default max_sigma handling in scripts/check_perf_results.sql#L24. Confirm how the threshold is passed to the performance check, then validate that a higher threshold reduces false-positive regression reports without disabling meaningful detection.

Written by the indexing model from the issue text.