JAL-2116 fix typo in build.xml for j2se element

diff --git a/build.xml b/build.xml
index 6ed340d..94f32fd 100755 (executable)
--- a/build.xml
+++ b/build.xml
@@ -426,7 +426,7 @@
         </information>
         <resources>
           <j2se version="9+" />
-          <j2se version="7,8" initial-heap-size="${inih}" max-heap-size="${maxh}" />
+          <j2se version="7,8" initial_heap_size="${inih}" max_heap_size="${maxh}" />
           <jar main="true" href="jalview.jar"/>
           <fileset dir="${packageDir}">
             <exclude name="jalview.jar" />