Remove explicit Spring Security 5.1.0.BUILD-SNAPSHOT

This is not needed since Spring Boot 2.1.0.BUILD-SNAPSHOT brings in
Spring Security 5.1.0.BUILD-SNAPSHOT.

Author: rwinch

pom.xml

@@ -22,7 +22,6 @@
         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
         <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
         <java.version>1.8</java.version>
-        <spring-security.version>5.1.0.BUILD-SNAPSHOT</spring-security.version>
         <frontend-maven-plugin.version>1.6</frontend-maven-plugin.version>
         <node.version>v10.6.0</node.version>
         <yarn.version>v1.8.0</yarn.version>