Update plugin org.springframework.boot to v3.5.4

Author: renovate[bot]

build.gradle.kts

@@ -1,6 +1,6 @@
 plugins {
 java
-id("org.springframework.boot") version "3.5.3"
+id("org.springframework.boot") version "3.5.4"
 id("io.spring.dependency-management") version "1.1.7"
 id("checkstyle")
 }