Removes unused file

etc/build/github-build.properties

@@ -1,13 +0,0 @@
-mxgraph2.dir=${basedir}/../../../mxgraph2
-jscompiler=${mxgraph2.dir}/etc/build/compiler.jar
-grapheditor.dir=${mxgraph2.dir}/javascript/examples/grapheditor/www/js
-src.dir=${basedir}/../../src
-war.dir=${basedir}/../../war
-javac.dir=${war.dir}/WEB-INF/classes
-build.dir=${basedir}/../../build
-war.name=draw.war
-imageexport.dir=${basedir}/../imageexport
-local.repo=${basedir}/../../build/diagramly-git
-username=jgraph
-remote.repo.name=draw.io
-desktop.dir=${basedir}/../chrome/desktop