Fix top nav on dagit Runs
Repair the collapsing top nav on the dagit Runs page in Safari by preventing the nav flex item from shrinking.
Additionally, remove the min-height from ScrollContainer -- from what I can tell, we don't need it. Please correct me if this is not the case. :)
View dagit Runs in Chrome/Safari. Verify that the nav does not vertically shrink for any window height.
Also verify that other ScrollContainer use cases seem to be operating fine without the min-height value.
Reviewers: alangenfeld, bengotow, prha, sashank
Reviewed By: prha
Differential Revision: https://dagster.phacility.com/D4426