[fenix] For https://github.com/mozilla-mobile/fenix/issues/22812 - Remove unused shadow attribute

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

@@ -105,7 +105,6 @@
     <color name="tab_ring_normal_theme">@color/accent_normal_theme</color>
     <color name="neutral_normal_theme">@color/photonGrey20</color>
     <color name="neutral_faded_normal_theme">#1FFBFBFE</color>
-    <color name="shadow_normal_theme">#050505</color>
     <color name="destructive_normal_theme">@color/photonRed40</color>
     <color name="disabled_normal_theme">#66FBFBFE</color>
     <color name="scrimStart_normal_theme">#F520123A</color>

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

@@ -19,7 +19,6 @@
     <attr name="inset" format="reference" />
     <attr name="neutral" format="reference" />
     <attr name="neutralFaded" format="reference" />
-    <attr name="shadow" format="reference" />
     <attr name="destructive" format="reference"/>
     <attr name="disabled" format="reference" />
     <attr name="scrimStart" format="reference"/>

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

@@ -137,7 +137,6 @@
     <color name="tab_ring_private_theme">#F565FF</color>
     <color name="neutral_private_theme">@color/photonGrey20</color>
     <color name="neutral_faded_private_theme">#1FFBFBFE</color>
-    <color name="shadow_private_theme">#2B1067</color>
     <color name="destructive_private_theme">@color/photonRed40</color>
     <color name="disabled_private_theme">#66FBFBFE</color>
     <color name="scrimStart_private_theme">#F520123A</color>
@@ -183,7 +182,6 @@
     <color name="tab_ring_normal_theme">@color/accent_light_theme</color>
     <color name="neutral_normal_theme">@color/photonGrey30</color>
     <color name="neutral_faded_normal_theme">@color/photonGrey20</color>
-    <color name="shadow_normal_theme">#1F000000</color>
     <color name="destructive_normal_theme">@color/photonRed70</color>
     <color name="disabled_normal_theme">#6620123A</color>
     <color name="scrimStart_normal_theme">#F515141A</color>

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

@@ -52,7 +52,6 @@
         <item name="tabRing">@color/tab_ring_normal_theme</item>
         <item name="neutral">@color/neutral_normal_theme</item>
         <item name="neutralFaded">@color/neutral_faded_normal_theme</item>
-        <item name="shadow">@color/shadow_normal_theme</item>
         <item name="destructive">@color/destructive_normal_theme</item>
         <item name="disabled">@color/disabled_normal_theme</item>
         <item name="scrimStart">@color/scrimStart_normal_theme</item>
@@ -237,7 +236,6 @@
         <item name="tabRing">@color/tab_ring_private_theme</item>
         <item name="neutral">@color/neutral_private_theme</item>
         <item name="neutralFaded">@color/neutral_faded_private_theme</item>
-        <item name="shadow">@color/shadow_private_theme</item>
         <item name="destructive">@color/destructive_private_theme</item>
         <item name="disabled">@color/disabled_private_theme</item>
         <item name="scrimStart">@color/scrimStart_private_theme</item>