Update pending reivew bg color on dark theme

Author: donokuda

src/GitHub.VisualStudio.UI/Styles/ThemeDark.xaml

@@ -63,6 +63,6 @@
   <SolidColorBrush x:Key="GitHubDiffGlyphFill.None" Color="#569CD6" />
 
   <SolidColorBrush x:Key="GitHubPeekViewBackground" Color="#252526" />
-  <SolidColorBrush x:Key="GitHubPendingReviewBackground" Color="#FFF8C7" />
+  <SolidColorBrush x:Key="GitHubPendingReviewBackground" Color="#26384D" />
   <SolidColorBrush x:Key="GitHubMultilineListItemActiveBrush" Color="#FF3F3F46"/>
 </ResourceDictionary>