SpeedscopeRenderer: fix code for black, isort
SpeedscopeRenderer: fix code for black, isort

This commit changes the SpeedscopeRenderer code to comply with project
style guidelines regarding code formatting with black and isort.

joerick/pyinstrument,joerick/pyinstrument,joerick/pyinstrument,joerick/pyinstrument,joerick/pyinstrument,joerick/pyinstrument