Set better default size for new field dialog

Author: NathanW2

src/ui/qgsaddattrdialogbase.ui

@@ -6,8 +6,8 @@
    <rect>
     <x>0</x>
     <y>0</y>
-    <width>267</width>
-    <height>267</height>
+    <width>225</width>
+    <height>190</height>
    </rect>
   </property>
   <property name="windowTitle">