[RPP Observations] Fix scroll bar bug when logs are empty

This was causing an extra scroll bar to appear on the logs section
when it isn't necessary.

Bug: None
Change-Id: Ie0204553521641d4a6bb4617f1bc5e70dcca3cf2
Reviewed-on: https://chromium-review.googlesource.com/c/devtools/devtools-frontend/+/6182535
Auto-Submit: Adam Raine <[email protected]>
Reviewed-by: Connor Clark <[email protected]>
Commit-Queue: Connor Clark <[email protected]>

Author: Adam Raine

front_end/panels/timeline/components/liveMetricsView.css

@@ -139,7 +139,7 @@
   display: flex;
   flex-direction: column;
   flex: 1 0 300px;
-  overflow: auto;
+  overflow: hidden;
   max-height: max-content;
 
   --app-color-toolbar-background: transparent;