Update to Spring Boot 2.5.0

To keep this getting started project aligned with upstream, we should
bump to the latest version.

As part of this, we also need to bump the Gradle Wrapper to at least
6.8. However, we're able to bump to Gradle 7.0 as there's nothing else
to do.

README.adoc

-:spring_boot_version: 2.4.4
+:spring_boot_version: 2.5.0
 :spring-boot: https://github.com/spring-projects/spring-boot
 :toc:
 :icons: font
@@ -54,7 +54,7 @@ them to your application context.
 [[scratch]]
 == Starting with Spring Initializr
 
-If you use Maven, visit the https://start.spring.io/#!type=maven-project&language=java&platformVersion=2.4.4&packaging=jar&jvmVersion=1.8&groupId=com.example&artifactId=spring-boot&name=spring-boot&description=Demo%20project%20for%20Spring%20Boot&packageName=com.example.spring-boot&dependencies=web[Spring Initializr] to generate a new project with the required dependencies (Spring Web).
+If you use Maven, visit the https://start.spring.io/#!type=maven-project&language=java&platformVersion=2.5.0&packaging=jar&jvmVersion=1.8&groupId=com.example&artifactId=spring-boot&name=spring-boot&description=Demo%20project%20for%20Spring%20Boot&packageName=com.example.spring-boot&dependencies=web[Spring Initializr] to generate a new project with the required dependencies (Spring Web).
 
 The following listing shows the `pom.xml` file that is created when you choose Maven:
 
@@ -65,7 +65,7 @@ include::initial/pom.xml[]
 ----
 ====
 
-If you use Gradle, visit the https://start.spring.io/#!type=gradle-project&language=java&platformVersion=2.4.4&packaging=jar&jvmVersion=1.8&groupId=com.example&artifactId=spring-boot&name=spring-boot&description=Demo%20project%20for%20Spring%20Boot&packageName=com.example.spring-boot&dependencies=web[Spring Initializr] to generate a new project with the required dependencies (Spring Web).
+If you use Gradle, visit the https://start.spring.io/#!type=gradle-project&language=java&platformVersion=2.5.0&packaging=jar&jvmVersion=1.8&groupId=com.example&artifactId=spring-boot&name=spring-boot&description=Demo%20project%20for%20Spring%20Boot&packageName=com.example.spring-boot&dependencies=web[Spring Initializr] to generate a new project with the required dependencies (Spring Web).
 
 The following listing shows the `build.gradle` file that is created when you choose Gradle:
 

complete/build.gradle

 plugins {
-	id 'org.springframework.boot' version '2.4.4'
+	id 'org.springframework.boot' version '2.5.0'
 	id 'io.spring.dependency-management' version '1.0.11.RELEASE'
 	id 'java'
 }

complete/gradle/wrapper/gradle-wrapper.properties

 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-6.5.1-bin.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-7.0-bin.zip
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists

complete/pom.xml

@@ -5,7 +5,7 @@
 	<parent>
 		<groupId>org.springframework.boot</groupId>
 		<artifactId>spring-boot-starter-parent</artifactId>
-		<version>2.4.4</version>
+		<version>2.5.0</version>
 		<relativePath/> <!-- lookup parent from repository -->
 	</parent>
 	<groupId>com.example</groupId>

initial/build.gradle

 plugins {
-	id 'org.springframework.boot' version '2.4.4'
+	id 'org.springframework.boot' version '2.5.0'
 	id 'io.spring.dependency-management' version '1.0.11.RELEASE'
 	id 'java'
 }

initial/gradle/wrapper/gradle-wrapper.properties

 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-6.5.1-bin.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-7.0-bin.zip
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists

initial/pom.xml

@@ -5,7 +5,7 @@
 	<parent>
 		<groupId>org.springframework.boot</groupId>
 		<artifactId>spring-boot-starter-parent</artifactId>
-		<version>2.4.4</version>
+		<version>2.5.0</version>
 		<relativePath/> <!-- lookup parent from repository -->
 	</parent>
 	<groupId>com.example</groupId>