Rephrase warning to prevent weird rendering issue

Author: Girgias

reference/datetime/dateperiod/construct.xml

@@ -24,14 +24,17 @@
    <methodparam choice="opt"><type>int</type><parameter>options</parameter><initializer>0</initializer></methodparam>
   </constructorsynopsis>
   <warning>
+   <simpara>
+    The following constructor variant has been deprecated:
+   </simpara>
    <constructorsynopsis role="DatePeriod">
     <modifier>public</modifier> <methodname>DatePeriod::__construct</methodname>
     <methodparam><type>string</type><parameter>isostr</parameter></methodparam>
     <methodparam choice="opt"><type>int</type><parameter>options</parameter><initializer>0</initializer></methodparam>
    </constructorsynopsis>
    <simpara>
-    This variant of the constructor has been deprecated, use
-    <methodname>DatePeriod::createFromISO8601String</methodname> instead.
+    Instead the <methodname>DatePeriod::createFromISO8601String</methodname>
+    static factory method should be used.
    </simpara>
   </warning>
   <para>