Update build.xml

A '=' sign was missing in the comment which makes a little confusion for beginners.

appinventor/components/build.xml

@@ -168,7 +168,7 @@
     <copy toFile="${public.deps.dir}/CommonVersion.jar" file="${build.dir}/common/CommonVersion.jar" />
 
     <!-- Add extension libraries here -->
-    <!-- Example: <copy toFile"${public.deps.dir}/my-dependency.jar" file="${lib.dir}/my-dependency/my-dependency-1.0.0.jar" /> -->
+    <!-- Example: <copy toFile="${public.deps.dir}/my-dependency.jar" file="${lib.dir}/my-dependency/my-dependency-1.0.0.jar" /> -->
     <!-- Remember to include my-dependency.jar in the @UsesLibraries annotation in the extension -->
   </target>