Update to Spring Boot 2.4.2

Closes gh-9443

gradle.properties

@@ -1,7 +1,7 @@
 aspectjVersion=1.9.6
 gaeVersion=1.9.82
 springJavaformatVersion=0.0.25
-springBootVersion=2.4.0
+springBootVersion=2.4.2
 version=5.5.0-SNAPSHOT
 kotlinVersion=1.4.10
 org.gradle.jvmargs=-Xmx3g -XX:MaxPermSize=2048m -XX:+HeapDumpOnOutOfMemoryError