ManifestParserTest: Don't use deprecated StringBufferInputStream

Replace it with ByteArrayInputStream as suggested in [1].

[1] http://stackoverflow.com/a/2219543/381622

Change-Id: I5ca8d721a756a82ea5f5687a20555303eb1dfc18
Signed-off-by: David Pursehouse <david.pursehouse@sonymobile.com>

org.eclipse.jgit.test/tst/org/eclipse/jgit/gitrepo/ManifestParserTest.java

 package org.eclipse.jgit.gitrepo;
 
 import static org.junit.Assert.assertTrue;
+import static java.nio.charset.StandardCharsets.UTF_8;
 
-import java.io.StringBufferInputStream;
+import java.io.ByteArrayInputStream;
 import java.util.HashSet;
 import java.util.Set;
 
 
 		ManifestParser parser = new ManifestParser(
 				null, null, "master", baseUrl, null, null);
-		parser.read(new StringBufferInputStream(xmlContent.toString()));
+		parser.read(new ByteArrayInputStream(xmlContent.toString().getBytes(UTF_8)));
 		// Unfiltered projects should have them all.
 		results.clear();
 		results.add("foo");