Merge #16113: gui: move coin control "OK" to the right hand side of the dialog

d595b4a gui: move coin control OK to the right (fanquake)

Pull request description:

  Fixes #16101

  The simplest fix seems to be to just drop the `sizePolicy` property, as we don't use that on any other instances of `QDialogButtonBox`.

  master (76e2cde):
  ![master](https://user-images.githubusercontent.com/863730/58490351-fc26d380-813a-11e9-9906-043ff4f4959f.png)

  This PR:
  ![right-side](https://user-images.githubusercontent.com/863730/58490360-00eb8780-813b-11e9-80fb-2dab04a5ba54.png)

ACKs for commit d595b4:
  hebasto:
    utACK d595b4a
  jonasschnelli:
    utACK d595b4a
  JosuGZ:
    tACK d595b4a

Tree-SHA512: 7099e21d58457bfcbc83237f5a47ddf18cfa6bd9d6194b357b314b4d54aed72fdbbf10cbe38223affd87c2542b8f364d37ce6a175e594dfbcd18c725b42a6d3e

Author: jonasschnelli

src/qt/forms/coincontroldialog.ui

@@ -467,12 +467,6 @@
    </item>
    <item>
     <widget class="QDialogButtonBox" name="buttonBox">
-     <property name="sizePolicy">
-      <sizepolicy hsizetype="Maximum" vsizetype="Fixed">
-       <horstretch>0</horstretch>
-       <verstretch>0</verstretch>
-      </sizepolicy>
-     </property>
      <property name="orientation">
       <enum>Qt::Horizontal</enum>
      </property>