Raise minimum supported version of Gradle to 4.10 and encourage use of 5.x

Closes gh-16681

spring-boot-project/spring-boot-docs/src/main/asciidoc/build-tool-plugins.adoc

@@ -169,7 +169,8 @@ Advanced configuration options and examples are available in the
 == Spring Boot Gradle Plugin
 The Spring Boot Gradle Plugin provides Spring Boot support in Gradle, letting you package
 executable jar or war archives, run Spring Boot applications, and use the dependency
-management provided by `spring-boot-dependencies`. It requires Gradle 4.4 or later. Please
+management provided by `spring-boot-dependencies`. It requires Gradle 5.x (4.10 is also
+supported but this support is deprecated and will be removed in a future release). Please
 refer to the plugin's documentation to learn more:
 
 * Reference ({spring-boot-gradle-plugin}/reference/html[HTML] and

spring-boot-project/spring-boot-docs/src/main/asciidoc/getting-started.adoc

@@ -52,7 +52,7 @@ Explicit build support is provided for the following build tools:
 |3.3+
 
 |Gradle
-|4.4+
+|5.x (4.10 is also supported but in a deprecated form)
 |===
 
 
@@ -201,8 +201,9 @@ scope.
 
 [[getting-started-gradle-installation]]
 ==== Gradle Installation
-Spring Boot is compatible with Gradle 4.4 and later. If you do not already have Gradle
-installed, you can follow the instructions at https://gradle.org.
+Spring Boot is compatible with 5.x. 4.10 is also supported but this support is deprecated
+and will be removed in a future release. 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`.
 Typically, your project declares dependencies to one or more