retrace_restricted_traces: Remove unused code. Remove unused load_json_metadata, get_trace_metadata and replace_metadata functions. Remove unused re import and trace_path parameter from get_context. Bug: angleproject:7107 Change-Id: I203609ca45145cdced8295d5edf7faa0c8606ae6 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3571883 Reviewed-by: Jamie Madill <jmadill@chromium.org> Commit-Queue: Lubosz Sarnecki <lubosz.sarnecki@collabora.com>