Bump springframework.version in /SpringRestDemo (#5)

Bumps `springframework.version` from 4.3.0.RELEASE to 5.2.6.RELEASE.

Updates `spring-core` from 4.3.0.RELEASE to 5.2.6.RELEASE
- [Release notes](https://github.com/spring-projects/spring-framework/releases)
- [Commits](spring-projects/spring-framework@v4.3.0.RELEASE...v5.2.6.RELEASE)

Updates `spring-web` from 4.3.0.RELEASE to 5.2.6.RELEASE
- [Release notes](https://github.com/spring-projects/spring-framework/releases)
- [Commits](spring-projects/spring-framework@v4.3.0.RELEASE...v5.2.6.RELEASE)

Updates `spring-webmvc` from 4.3.0.RELEASE to 5.2.6.RELEASE
- [Release notes](https://github.com/spring-projects/spring-framework/releases)
- [Commits](spring-projects/spring-framework@v4.3.0.RELEASE...v5.2.6.RELEASE)

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SpringRestDemo/pom.xml

@@ -18,7 +18,7 @@
 		<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
 		<maven.compiler.source>1.7</maven.compiler.source>
 		<maven.compiler.target>1.7</maven.compiler.target>
-		<springframework.version>4.3.0.RELEASE</springframework.version>
+		<springframework.version>5.2.6.RELEASE</springframework.version>
 		<jackson.library>2.11.0</jackson.library>
 		<!-- <jersey.version>2.30.1</jersey.version> -->
 	</properties>