Add missing @since tag for replaceLineBreaksWithSpace

Change-Id: Ibd9d9ba609a2cd7707b985cdb07405dce0422aab
Signed-off-by: Robin Stocker <robin@nibor.org>

org.eclipse.jgit/src/org/eclipse/jgit/util/StringUtils.java

@@ -286,6 +286,7 @@ public final class StringUtils {
 	 * @param in
 	 *            A string with line breaks
 	 * @return in without line breaks
+	 * @since 3.1
 	 */
 	public static String replaceLineBreaksWithSpace(String in) {
 		char[] buf = new char[in.length()];