Remove non-existing source directories from Java 7 test build

This was a copy-artifact when the bundle was created. This chanhe
removed some warnings in Eclipse.

Change-Id: I32acdf4b60bf5528566e66b1fd82113b1343ed37

org.eclipse.jgit.java7.test/build.properties

-source.. = tst/,\
-	   tst-rsrc/,\
-	   exttst/
 bin.includes = META-INF/,\
 	       .,\
 	       plugin.properties