Raise the minimum supported version of Gradle to 8.4

Closes gh-42481

Author: wilkinsona

spring-boot-project/spring-boot-docs/src/docs/antora/modules/ROOT/pages/installing.adoc

@@ -49,7 +49,7 @@ More details on getting started with Spring Boot and Maven can be found in the x
 [[getting-started.installing.java.gradle]]
 === Gradle Installation
 
-Spring Boot is compatible with Gradle 7.x (7.6.4 or later) or 8.x (8.3 or later).
+Spring Boot is compatible with Gradle 7.x (7.6.4 or later) or 8.x (8.4 or later).
 If you do not already have Gradle installed, you can follow the instructions at https://gradle.org.
 
 Spring Boot dependencies can be declared by using the `org.springframework.boot` `group`.

spring-boot-project/spring-boot-docs/src/docs/antora/modules/ROOT/pages/system-requirements.adoc

@@ -13,7 +13,7 @@ Explicit build support is provided for the following build tools:
 | 3.6.3 or later
 
 | Gradle
-| Gradle 7.x (7.6.4 or later) or 8.x (8.3 or later)
+| Gradle 7.x (7.6.4 or later) or 8.x (8.4 or later)
 |===
 
 

spring-boot-project/spring-boot-tools/spring-boot-gradle-plugin/src/docs/antora/modules/gradle-plugin/pages/introduction.adoc

@@ -3,6 +3,6 @@
 
 The Spring Boot Gradle Plugin provides Spring Boot support in https://gradle.org[Gradle].
 It allows you to package executable jar or war archives, run Spring Boot applications, and use the dependency management provided by `spring-boot-dependencies`.
-Spring Boot's Gradle plugin requires Gradle 7.x (7.6.4 or later) or 8.x (8.3 or later) and can be used with Gradle's {url-gradle-docs}/configuration_cache.html[configuration cache].
+Spring Boot's Gradle plugin requires Gradle 7.x (7.6.4 or later) or 8.x (8.4 or later) and can be used with Gradle's {url-gradle-docs}/configuration_cache.html[configuration cache].
 
 In addition to this user guide, xref:api/java/index.html[API documentation] is also available.

spring-boot-project/spring-boot-tools/spring-boot-gradle-test-support/src/main/java/org/springframework/boot/testsupport/gradle/testkit/GradleVersions.java

@@ -42,7 +42,7 @@ public static List<String> allCompatible() {
 		if (isJavaVersion(JavaVersion.VERSION_21)) {
 			return Arrays.asList("8.5", GradleVersion.current().getVersion());
 		}
-		return Arrays.asList("7.6.4", "8.3", GradleVersion.current().getVersion());
+		return Arrays.asList("7.6.4", "8.4", GradleVersion.current().getVersion());
 	}
 
 	public static String minimumCompatible() {