Merge pull request spring-projects#522 from vbadipat

* pr/522:
  Polish "Use https for Maven XSD"
  Use https for Maven XSD

Closes spring-projectsgh-522

pom.xml

@@ -1,7 +1,7 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <project xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
   xmlns="http://maven.apache.org/POM/4.0.0"
-  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/maven-v4_0_0.xsd">
+  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
   <modelVersion>4.0.0</modelVersion>
   <groupId>org.springframework.samples</groupId>
   <artifactId>spring-petclinic</artifactId>