Make trace seeking UTF-8 characters aware

This is raised in https://gitlab.com/gitlab-org/gitlab-ce/issues/30721#note_27275401

The error: https://sentry.gitlap.com/gitlab/devgitlaborg/issues/26227/

Encoding::UndefinedConversionError: "\xC3" from ASCII-8BIT to UTF-8

From: app/controllers/projects/builds_controller.rb in block in trace at line 43