BrowserHtmlDebugTrait should set correct permissions on created files

I can't reproduce this, I think it would be dependent on file system permissions on the directory?

I created a fresh browser_output directory locally and ran a test and permissions were fine. Was able to delete the html output without sudo

adam@8fa2a3a71304:data $ ls -al app/sites/simpletest/browser_output/
total 68
drwxr-xr-x    2 adam     adam          4096 Aug 15 03:07 .
drwxr-xr-x  152 adam     adam          4096 Aug 15 03:07 ..
-rw-r--r--    1 adam     adam            55 Aug 15 03:07 .htaccess
-rw-r--r--    1 adam     adam          3567 Aug 15 03:07 Drupal_Tests_node_Functional_NodeAccessCacheabilityTest-1-84119625.html