Fix use of : in label (violation of HIG)

(cherry-picked from 5a20313)

Author: nyalldawson

src/ui/composer/qgscomposerlegendwidgetbase.ui

@@ -130,7 +130,7 @@
           <item row="1" column="0">
            <widget class="QLabel" name="label_15">
             <property name="text">
-             <string>Title alignment:</string>
+             <string>Title alignment</string>
             </property>
            </widget>
           </item>