[GM3Restyling] Update Performance flame chart tooltip styles

Screenshot: https://imgur.com/a/DrPAtHE

Bug: 406466030
Change-Id: Ic43622bf72aea0e9de25c419b2b83799b968be2c
Reviewed-on: https://chromium-review.googlesource.com/c/devtools/devtools-frontend/+/6397058
Auto-Submit: Kateryna Prokopenko <[email protected]>
Commit-Queue: Kim-Anh Tran <[email protected]>
Reviewed-by: Kim-Anh Tran <[email protected]>

Author: Kateryna Prokopenko

front_end/panels/timeline/timelineFlameChartView.css

@@ -130,7 +130,8 @@
   contain: content;
   background-color: var(--sys-color-cdt-base-container);
   pointer-events: none;
-  padding: 4px 8px;
+  padding: var(--sys-size-6) var(--sys-size-8);
+  border-radius: var(--sys-shape-corner-small);
   white-space: nowrap;
   max-width: 80%;
   box-shadow: var(--drop-shadow);