Fix Amoled navigation bar colour on OxygenOS (#1762)

app/src/main/res/values-v21/themes.xml

@@ -37,7 +37,7 @@
         <!-- Attributes specific for SDK 21 and up  -->
         <item name="android:windowDrawsSystemBarBackgrounds">true</item>
         <item name="android:statusBarColor">@android:color/transparent</item>
-        <item name="android:navigationBarColor">@color/colorAmoledPrimary</item>
+        <item name="android:navigationBarColor">@android:color/transparent</item>
     </style>
 
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