Update tab hover colors (#13434)

The hover tab color used to be generated from the selected tab color, which would end up lighter or darker, and white-gray colors would end up pink.
It is now simply the selected tab color with 60% opacity. This is also how brushes are created for accent buttons and color buttons (although with different opacity levels).

(cherry picked from commit c6b67aa)
Service-Card-Id: 83894208
Service-Version: 1.15

src/cascadia/TerminalApp/TerminalTab.cpp

@@ -1452,18 +1452,16 @@ namespace winrt::TerminalApp::implementation
             subtleFillColorTertiaryBrush.Color(subtleFillColorTertiary);
         }
 
-        hoverTabBrush.Color(TerminalApp::ColorHelper::GetAccentColor(color));
         selectedTabBrush.Color(color);
 
         // currently if a tab has a custom color, a deselected state is
         // signified by using the same color with a bit of transparency
-        auto deselectedTabColor = color;
-        deselectedTabColor.A = 64;
-        deselectedTabBrush.Color(deselectedTabColor);
+        deselectedTabBrush.Color(color);
+        deselectedTabBrush.Opacity(0.3);
+
+        hoverTabBrush.Color(color);
+        hoverTabBrush.Opacity(0.6);
 
-        // currently if a tab has a custom color, a deselected state is
-        // signified by using the same color with a bit of transparency
-        //
         // Prior to MUX 2.7, we set TabViewItemHeaderBackground, but now we can
         // use TabViewItem().Background() for that. HOWEVER,
         // TabViewItem().Background() only sets the color of the tab background