Project File Source test fails after Chrome version upgrade

Since 2021-04-16 web_project_file_source started to fail. It appears to be due to the SiteSpeed and Chrome version update similarly to #7 (comment 458926060).

• Last successful run: https://gitlab.com/gitlab-org/quality/performance-sitespeed/-/pipelines/269368402 - GitLab version: 13.11.0-pre 11c635a843b, Chrome Google Chrome 89.0.4389.82
• First failure: https://gitlab.com/gitlab-org/quality/performance-sitespeed/-/jobs/1185336971#L338 - GitLab version: 13.11.0-pre b17c41f4186, Chrome Google Chrome 90.0.4430.72

When running the test using Docker SHA from last successful run sitespeedio/sitespeed.io@sha256:3adbff57347a4c4e3dc95172684d403ca0f03e3d6102a826242d8d98baa1ef6a, the test passes:

NAME                    | FCP (ms) | LCP (ms)        | TBT (ms)       | SI (ms) | LVC (ms) | TFR SIZE (kb) | SCORE | RESULT
------------------------|----------|-----------------|----------------|---------|----------|---------------|-------|-------
web_project_file_source | 851      | ✓ 9775 (<11500) | ✓ 4859 (<8500) | 1665    | 9767     | 7927.6        | 67    | Passed