refactor(#328): 불필요한 undo 버튼 제거

Author: hegleB

AOS/app/src/main/res/layout/fragment_mind_map.xml

@@ -28,7 +28,7 @@
             android:layout_width="0dp"
             android:layout_height="0dp"
             android:visibility="@{vm.selectedNode != null ? View.VISIBLE : View.GONE}"
-            app:constraint_referenced_ids="imgbtn_mind_map_add,imgbtn_mind_map_back,imgbtn_mind_map_remove,imgbtn_mind_map_edit,view_mind_map_side_bar"
+            app:constraint_referenced_ids="imgbtn_mind_map_add,imgbtn_mind_map_remove,imgbtn_mind_map_edit,view_mind_map_side_bar"
             app:layout_constraintBottom_toBottomOf="@id/view_mind_map_side_bar"
             app:layout_constraintEnd_toEndOf="@id/view_mind_map_side_bar"
             app:layout_constraintStart_toStartOf="@id/view_mind_map_side_bar"
@@ -74,23 +74,11 @@
             android:background="@android:color/transparent"
             android:src="@drawable/ic_outlined_drawing"
             app:layout_constraintBottom_toBottomOf="@id/view_mind_map_side_bar"
-            app:layout_constraintEnd_toStartOf="@id/imgbtn_mind_map_back"
+            app:layout_constraintEnd_toEndOf="parent"
             app:layout_constraintHorizontal_chainStyle="spread"
             app:layout_constraintStart_toEndOf="@id/imgbtn_mind_map_remove"
             app:layout_constraintTop_toTopOf="@id/view_mind_map_side_bar" />
 
-        <ImageButton
-            android:id="@+id/imgbtn_mind_map_back"
-            android:layout_width="25dp"
-            android:layout_height="25dp"
-            android:background="@android:color/transparent"
-            android:src="@drawable/ic_undo"
-            app:layout_constraintBottom_toBottomOf="@id/view_mind_map_side_bar"
-            app:layout_constraintEnd_toEndOf="@id/view_mind_map_side_bar"
-            app:layout_constraintHorizontal_chainStyle="spread"
-            app:layout_constraintStart_toEndOf="@id/imgbtn_mind_map_edit"
-            app:layout_constraintTop_toTopOf="@id/view_mind_map_side_bar" />
-
 
     </androidx.constraintlayout.widget.ConstraintLayout>
-</layout>
+</layout>