Remove redundant margin properties

Those are the same with the default values.

src/gui/aboutdialog.ui

@@ -489,7 +489,6 @@
    </item>
   </layout>
  </widget>
- <layoutdefault spacing="6" margin="11"/>
  <resources/>
  <connections/>
 </ui>

src/gui/optionsdialog.ui

@@ -561,9 +561,6 @@
                </item>
                <item>
                 <layout class="QHBoxLayout" name="horizontalLayout_8">
-                 <property name="topMargin">
-                  <number>0</number>
-                 </property>
                  <item>
                   <widget class="QCheckBox" name="checkFileLogBackup">
                    <property name="text">
@@ -604,9 +601,6 @@
                </item>
                <item>
                 <layout class="QHBoxLayout" name="horizontalLayout_9">
-                 <property name="topMargin">
-                  <number>0</number>
-                 </property>
                  <item>
                   <widget class="QCheckBox" name="checkFileLogDelete">
                    <property name="text">
@@ -730,9 +724,6 @@
                   <bool>true</bool>
                  </property>
                  <layout class="QVBoxLayout" name="verticalLayout_18">
-                  <property name="bottomMargin">
-                   <number>0</number>
-                  </property>
                   <item>
                    <widget class="QCheckBox" name="checkAdditionDialogFront">
                     <property name="text">
@@ -2274,9 +2265,6 @@
                <bool>false</bool>
               </property>
               <layout class="QGridLayout" name="gridLayout_2">
-               <property name="bottomMargin">
-                <number>9</number>
-               </property>
                <item row="0" column="0">
                 <widget class="QLabel" name="label_max_active_dl">
                  <property name="text">