pluralise variable

git-svn-id: https://svn.apache.org/repos/asf/ant/core/trunk@397089 13f79535-47bb-0310-9956-ffa450edef68

docs/manual/CoreTasks/property.html

@@ -14,7 +14,7 @@
 (by name and value), or set of properties (from file or
 resource) in the project.  Properties are case sensitive.</p>
  Properties are immutable: whoever sets a property first freezes it for the
- rest of the build; they are most definitely not variable.
+ rest of the build; they are most definitely not variables.
 <p>There are six ways to set properties:</p>
 <ul>
   <li>By supplying both the <i>name</i> and <i>value</i> attribute.</li>