TemporaryBufferTest: Open TemporaryBuffer in try-with-resource

Except the cases where the warning was suppressed in bf757cd because
they are explicitly testing functionality that is not possible in t-w-r.

Change-Id: I6c66eb31a2314028e09a9213dc695cd163f907e9
Signed-off-by: David Pursehouse <david.pursehouse@gmail.com>

org.eclipse.jgit.test/tst/org/eclipse/jgit/util/TemporaryBufferTest.java

@@ -404,8 +404,7 @@ public class TemporaryBufferTest {
 
 	@Test
 	public void testHeap() throws IOException {
-		@SuppressWarnings("resource" /* java 7 */)
+		try (TemporaryBuffer b = new TemporaryBuffer.Heap(2 * 8 * 1024)) {
-		final TemporaryBuffer b = new TemporaryBuffer.Heap(2 * 8 * 1024);
 			final byte[] r = new byte[8 * 1024];
 			b.write(r);
 			b.write(r);
@@ -416,6 +415,7 @@ public class TemporaryBufferTest {
 				assertEquals("In-memory buffer limit exceeded", e.getMessage());
 			}
 		}
+	}
 
 	@Test
 	public void testHeapWithEstimatedSize() throws IOException {