URL Cleanup

This commit updates URLs to prefer the https protocol. Redirects are not followed to avoid accidentally expanding intentionally shortened URLs (i.e. if using a URL shortener).

# Fixed URLs

## Fixed Success
These URLs were switched to an https URL with a 2xx status. While the status was successful, your review is still recommended.

* http://docs.spring.io/spring-framework/docs/ migrated to:
  https://docs.spring.io/spring-framework/docs/ ([https](https://docs.spring.io/spring-framework/docs/) result 200).
* http://docs.spring.io/spring-shell/docs/current/api/ migrated to:
  https://docs.spring.io/spring-shell/docs/current/api/ ([https](https://docs.spring.io/spring-shell/docs/current/api/) result 200).
* http://www.apache.org/licenses/LICENSE-2.0 migrated to:
  https://www.apache.org/licenses/LICENSE-2.0 ([https](https://www.apache.org/licenses/LICENSE-2.0) result 200).

# Ignored
These URLs were intentionally ignored.

* http://maven.apache.org/POM/4.0.0
* http://maven.apache.org/xsd/maven-4.0.0.xsd
* http://www.w3.org/2001/XMLSchema-instance

spring-cloud-stream-docs/pom.xml

@@ -107,10 +107,10 @@
 									</stylesheetfile>
 									<links>
 										<link>
-											http://docs.spring.io/spring-framework/docs/${spring.version}/javadoc-api/
+											https://docs.spring.io/spring-framework/docs/${spring.version}/javadoc-api/
 										</link>
 										<link>
-											http://docs.spring.io/spring-shell/docs/current/api/
+											https://docs.spring.io/spring-shell/docs/current/api/
 										</link>
 									</links>
 								</configuration>