Remove declared IOException which is no longer thrown

Since 2ccea7f0 ChangeIdUtil.computeChangeId() doesn't throw IOException
anymore.

Change-Id: I0bf43f2346dadbbfe7e6cbcb38b5525456fbf686
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

org.eclipse.jgit.junit/src/org/eclipse/jgit/junit/TestRepository.java

 			return self;
 		}
 
-		private void insertChangeId(org.eclipse.jgit.lib.CommitBuilder c)
-				throws IOException {
+		private void insertChangeId(org.eclipse.jgit.lib.CommitBuilder c) {
 			if (changeId == null)
 				return;
 			int idx = ChangeIdUtil.indexOfChangeId(message, "\n");

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

 
 import static org.junit.Assert.assertEquals;
 
-import java.io.IOException;
 import java.util.concurrent.TimeUnit;
 
 import org.eclipse.jgit.junit.MockSystemReader;
 	}
 
 	@Test
-	public void testId() throws IOException {
+	public void testId() {
 		String msg = "A\nMessage\n";
 		ObjectId id = ChangeIdUtil.computeChangeId(treeId, parentId, p, q, msg);
 		assertEquals("73f3751208ac92cbb76f9a26ac4a0d9d472e381b", ObjectId