Bump spring-framework-bom from 5.1.7.RELEASE to 5.1.8.RELEASE

Bumps [spring-framework-bom](https://github.com/spring-projects/spring-framework) from 5.1.7.RELEASE to 5.1.8.RELEASE.
- [Release notes](https://github.com/spring-projects/spring-framework/releases)
- [Commits](spring-projects/spring-framework@v5.1.7.RELEASE...v5.1.8.RELEASE)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

pom.xml

@@ -56,7 +56,7 @@
         <maven.compiler.source>${java.version}</maven.compiler.source>
         <maven.compiler.target>${java.version}</maven.compiler.target>
         <slf4j.version>1.7.26</slf4j.version>
-        <spring.version>5.1.7.RELEASE</spring.version>
+        <spring.version>5.1.8.RELEASE</spring.version>
         <spring-boot.version>2.1.5.RELEASE</spring-boot.version>
         <junit-platform.version>1.4.2</junit-platform.version>
         <junit-jupiter.version>5.4.2</junit-jupiter.version>