[fenix] For https://github.com/mozilla-mobile/fenix/issues/24333 - Complete removing the broken code for focusing the newly created collection

The removal was initially scheduled to happen in the PR for https://github.com/mozilla-mobile/fenix/issues/24333
but landed separately in https://github.com/mozilla-mobile/fenix/pull/25045.
These are two small leftovers.

app/src/main/res/drawable/session_border.xml

@@ -1,9 +0,0 @@
-<?xml version="1.0" encoding="UTF-8"?>
-<!-- This Source Code Form is subject to the terms of the Mozilla Public
-   - License, v. 2.0. If a copy of the MPL was not distributed with this
-   - file, You can obtain one at http://mozilla.org/MPL/2.0/. -->
-
-<shape xmlns:android="http://schemas.android.com/apk/res/android">
-    <corners android:radius="@dimen/tab_corner_radius"/>
-    <stroke android:width="@dimen/tab_border_width" android:color="?accent"/>
-</shape>

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

@@ -14,7 +14,6 @@
     <dimen name="library_item_height">56dp</dimen>
     <dimen name="library_item_icon_margin_horizontal">16dp</dimen>
     <dimen name="history_favicon_width_height">40dp</dimen>
-    <dimen name="tab_border_width">2dp</dimen>
     <dimen name="tab_corner_radius">8dp</dimen>
     <dimen name="preference_icon_drawable_size">24dp</dimen>
     <dimen name="search_bar_search_engine_icon_padding">12dp</dimen>