Remove documentation for unsupported gradle versions

See gh-23562

spring-boot-project/spring-boot-docs/src/main/asciidoc/appendix-configuration-metadata.adoc

@@ -737,16 +737,7 @@ If you have defined `@ConfigurationProperties` in your application, make sure to
 	</project>
 ----
 
-With Gradle 4.5 and earlier, the dependency should be declared in the `compileOnly` configuration, as shown in the following example:
-
-[source,groovy,indent=0,subs="verbatim,quotes,attributes"]
-----
-	dependencies {
-		compileOnly "org.springframework.boot:spring-boot-configuration-processor"
-	}
-----
-
-With Gradle 4.6 and later, the dependency should be declared in the `annotationProcessor` configuration, as shown in the following example:
+With Gradle, the dependency should be declared in the `annotationProcessor` configuration, as shown in the following example:
 
 [source,groovy,indent=0,subs="verbatim,quotes,attributes"]
 ----