Update unserialize.xml Fix typo (#4328)

Author: mmalferov

reference/var/functions/unserialize.xml

@@ -196,7 +196,7 @@
        <entry>7.1.0</entry>
        <entry>
         The <literal>allowed_classes</literal> element of
-        <parameter>options</parameter>) is now strictly typed, i.e. if anything
+        <parameter>options</parameter> is now strictly typed, i.e. if anything
         other than an <type>array</type> or a <type>bool</type> is given,
         <function>unserialize</function> returns &false; and issues an
         <constant>E_WARNING</constant>.