Updating checkstyle rules to make sure header uses https

spring-cloud-build-tools/src/main/resources/checkstyle-header.txt

@@ -5,7 +5,7 @@
 ^\Q * you may not use this file except in compliance with the License.\E$
 ^\Q * You may obtain a copy of the License at\E$
 ^\Q *\E$
-^\Q *      http://www.apache.org/licenses/LICENSE-2.0\E$
+^\Q *      https://www.apache.org/licenses/LICENSE-2.0\E$
 ^\Q *\E$
 ^\Q * Unless required by applicable law or agreed to in writing, software\E$
 ^\Q * distributed under the License is distributed on an "AS IS" BASIS,\E$