Remove SuppressWarnings since currently ignored

The following warning was raised by Eclipse:
"At least one of the problems in category
'unused' is not analysed due to a compiler option being ignored"

The org.eclipse.jdt.core.compiler.problem.unusedTypeParameter compiler
option is set to ignore, hence the warning suppression is redundant.

Change-Id: I5fd6efc9968be133c71e95c53803c44310d75e85
diff --git a/org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/file/FileReftableStackTest.java b/org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/file/FileReftableStackTest.java
index 98e4b3e..6c79927 100644
--- a/org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/file/FileReftableStackTest.java
+++ b/org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/file/FileReftableStackTest.java
@@ -118,7 +118,7 @@
 		testCompaction(1024);
 	}
 
-	@SuppressWarnings({ "resource", "unused" })
+	@SuppressWarnings("resource")
 	@Test
 	public void missingReftable() throws Exception {
 		// Can't delete in-use files on Windows.