Merge pull request #375 from grails/renovate/spring-boot

Update spring boot to v2.5.5

Author: puneetbehl

gradle.properties

@@ -21,7 +21,7 @@ servletApiVersion=4.0.1
 slf4jVersion=1.7.32
 snakeyamlVersion=1.29
 spockVersion=2.0-groovy-3.0
-springBootVersion=2.5.4
+springBootVersion=2.5.5
 springVersion=5.3.10
 tomcatLog4jVersion=8.5.2
 tomcatVersion=9.0.53