Hide memory track by default

In https://bugzilla.mozilla.org/show_bug.cgi?id=1594756#c0 Olli said:
> When using the built-in profiler, memory measurements are shown by default in the profiles. The UI is already rather full of information, and memory measurements don't often tell anything too useful (when one is profiling some non-memory related perf issue).
> It would be nice to be able to hide Memory information by default.

┆Issue is synchronized with this [Jira Task](https://mozilla-hub.atlassian.net/browse/FP-216)