Disable bold tab text in dark mode by default.

Medium weight was causing text to shift, which was distracting.

Bug: 1011307
Fixes: 1011307
Change-Id: I4e879b34d9cf51a5f29fc96943569356ad207f94
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1850633Reviewed-by: Peter Kasting <pkasting@chromium.org>
Commit-Queue: Peter Kasting <pkasting@chromium.org>
Commit-Queue: Dana Fried <dfried@chromium.org>
Auto-Submit: Dana Fried <dfried@chromium.org>
Cr-Commit-Position: refs/heads/master@{#704398}

chrome/browser/ui/ui_features.cc

@@ -77,7 +77,7 @@ const base::Feature kTabOutlinesInLowContrastThemes{
 // Enables a more prominent active tab title in dark mode to aid with
 // accessibility.
 const base::Feature kProminentDarkModeActiveTabTitle{
-    "ProminentDarkModeActiveTabTitle", base::FEATURE_ENABLED_BY_DEFAULT};
+    "ProminentDarkModeActiveTabTitle", base::FEATURE_DISABLED_BY_DEFAULT};
 
 // Enables a web-based separator that's only used for performance testing. See
 // https://crbug.com/993502.