Remove spring-boot-gradle-plugin

Issue gh-9539

Author: rwinch

build.gradle

@@ -1,7 +1,6 @@
 buildscript {
 	dependencies {
 		classpath "io.spring.javaformat:spring-javaformat-gradle-plugin:$springJavaformatVersion"
-		classpath "org.springframework.boot:spring-boot-gradle-plugin:$springBootVersion"
 		classpath 'io.spring.nohttp:nohttp-gradle:0.0.5.RELEASE'
 		classpath "io.freefair.gradle:aspectj-plugin:5.0.1"
 		classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlinVersion"