Update spring boot to v2.7.3 (grails#588)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

gradle.properties

@@ -23,7 +23,7 @@ servletApiVersion=4.0.1
 slf4jVersion=1.7.36
 snakeyamlVersion=1.32
 spockVersion=2.1-groovy-3.0
-springBootVersion=2.7.0
+springBootVersion=2.7.3
 springVersion=5.3.20
 tomcatLog4jVersion=8.5.2
 tomcatVersion=9.0.65