[fenix] For https://github.com/mozilla-mobile/fenix/issues/21973 - Remove @color/synced_tabs_separator_dark_theme redirection

app/src/main/res/values-night/colors.xml

@@ -83,7 +83,7 @@
     <color name="top_sites_border_color">@color/photonDarkGrey90</color>
 
     <!-- Synced tabs colors-->
-    <color name="synced_tabs_separator">@color/synced_tabs_separator_dark_theme</color>
+    <color name="synced_tabs_separator">@color/photonDarkGrey10</color>
 
     <!-- Collection icons-->
     <color name="collection_icon_color_violet">@color/photonViolet40</color>

app/src/main/res/values/colors.xml

@@ -72,7 +72,6 @@
     <color name="disabled_dark_theme">#66FBFBFE</color>
     <color name="scrimStart_dark_theme">#F520123A</color>
     <color name="scrimEnd_dark_theme">#F515141A</color>
-    <color name="synced_tabs_separator_dark_theme">@color/photonDarkGrey10</color>
     <color name="top_site_title_text_dark_theme">@color/photonLightGrey05</color>
     <color name="toolbar_start_gradient_dark_theme">@color/foundation_dark_theme</color>
     <color name="toolbar_center_gradient_dark_theme">@color/foundation_dark_theme</color>