fix attachment remove button alignment

fixes #3597
Closes #4077
// FREEBIE

res/drawable/conversation_attachment_close_circle.xml

@@ -1,11 +1,5 @@
 <?xml version="1.0" encoding="utf-8"?>
 <layer-list xmlns:android="http://schemas.android.com/apk/res/android">
-    <item>
-        <shape android:shape="oval">
-            <size android:height="24dp" android:width="24dp"/>
-            <solid android:color="@color/white"/>
-        </shape>
-    </item>
     <item>
         <shape android:shape="oval">
             <size android:height="21dp" android:width="21dp"/>

res/layout/thumbnail_view.xml

@@ -6,8 +6,7 @@
                android:layout_height="match_parent"
                android:adjustViewBounds="true"
                android:scaleType="fitCenter"
-               android:contentDescription="@string/conversation_item__mms_image_description"
-               android:layout_margin="@dimen/media_bubble_border_width" />
+               android:contentDescription="@string/conversation_item__mms_image_description" />
 
     <ViewStub android:id="@+id/transfer_controls_stub"
               android:layout_width="70dp"

res/layout/thumbnail_view_remove_button.xml

@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="utf-8"?>
 <ImageView xmlns:android="http://schemas.android.com/apk/res/android"
            android:id="@+id/remove_image_button"
-           android:layout_width="wrap_content"
-           android:layout_height="wrap_content"
+           android:layout_width="@dimen/media_bubble_remove_button_size"
+           android:layout_height="@dimen/media_bubble_remove_button_size"
            android:src="@drawable/conversation_attachment_close_circle" />

res/values/dimens.xml

@@ -24,6 +24,7 @@
     <dimen name="message_bubble_shadow_distance">1.5dp</dimen>
     <dimen name="media_bubble_height">210dp</dimen>
     <dimen name="media_bubble_border_width">3dp</dimen>
+    <dimen name="media_bubble_remove_button_size">24dp</dimen>
 
     <integer name="media_overview_cols">3</integer>
     <dimen name="message_details_table_row_pad">10dp</dimen>