Center "Take photo" text in attachment selector

Fixes #4959
Closes #4961

res/layout/attachment_type_selector.xml

@@ -132,6 +132,7 @@
             <TextView android:layout_marginTop="10dp"
                       android:layout_width="wrap_content"
                       android:layout_height="wrap_content"
+                      android:gravity="center"
                       style="@style/AttachmentTypeLabel"
                       android:text="@string/attachment_type_selector__camera"/>
 
@@ -203,4 +204,4 @@
 
     </LinearLayout>
 
-</LinearLayout>
+</LinearLayout>