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 fixed successfully.

* http://repo.spring.io/milestone migrated to:
  https://repo.spring.io/milestone ([https](https://repo.spring.io/milestone) result 302).
* http://repo.spring.io/snapshot migrated to:
  https://repo.spring.io/snapshot ([https](https://repo.spring.io/snapshot) result 302).

# Ignored
These URLs were intentionally ignored.

* http://maven.apache.org/POM/4.0.0
* http://maven.apache.org/maven-v4_0_0.xsd
* http://www.w3.org/2001/XMLSchema-instance

Author: spring-operator

pom.xml

@@ -55,12 +55,12 @@
 		<repository>
 			<id>spring-snapshot</id>
 			<name>Spring Snapshot Repository</name>
-			<url>http://repo.spring.io/snapshot</url>
+			<url>https://repo.spring.io/snapshot</url>
 		</repository>
 		<repository>
 			<id>spring-milestone</id>
 			<name>Spring Milestone Repository</name>
-			<url>http://repo.spring.io/milestone</url>
+			<url>https://repo.spring.io/milestone</url>
 		</repository>
 	</repositories>
 	-->