Rename "Prefer encryption" to "Allow encryption"

Because it actually prefers non-encryption but allows it if requested.

src/gui/optionsdialog.ui

@@ -2190,7 +2190,7 @@
                   <widget class="QComboBox" name="comboEncryption">
                    <item>
                     <property name="text">
-                     <string>Prefer encryption</string>
+                     <string>Allow encryption</string>
                     </property>
                    </item>
                    <item>

src/webui/www/private/preferences_content.html

@@ -479,7 +479,7 @@
         <div class="formRow">
             <label for="encryption_select">QBT_TR(Encryption mode:)QBT_TR[CONTEXT=OptionsDialog]</label>
             <select id="encryption_select">
-                <option value="0">QBT_TR(Prefer encryption)QBT_TR[CONTEXT=OptionsDialog]</option>
+                <option value="0">QBT_TR(Allow encryption)QBT_TR[CONTEXT=OptionsDialog]</option>
                 <option value="1">QBT_TR(Require encryption)QBT_TR[CONTEXT=OptionsDialog]</option>
                 <option value="2">QBT_TR(Disable encryption)QBT_TR[CONTEXT=OptionsDialog]</option>
             </select>