Merge pull request #12365 from jacobis:fix-reference-guide

* pr/12365:
  Remove a redundant trailing slash in doc

Author: snicoll

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

@@ -189,7 +189,7 @@ scope.
 [[getting-started-gradle-installation]]
 ==== Gradle Installation
 Spring Boot is compatible with Gradle 4. If you do not already have Gradle installed, you
-can follow the instructions at https://gradle.org/.
+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