Drop the Grails 3 sample as it is incompatible with Framework 5

Closes gh-637

Author: wilkinsona

build.gradle

@@ -180,10 +180,6 @@ samples {
 	dependOn 'spring-restdocs-webtestclient:install'
 	dependOn 'spring-restdocs-asciidoctor:install'
 
-	restNotesGrails {
-		workingDir "$projectDir/samples/rest-notes-grails"
-	}
-
 	restNotesSpringHateoas {
 		workingDir "$projectDir/samples/rest-notes-spring-hateoas"
 	}

docs/src/docs/asciidoc/getting-started.adoc

@@ -44,11 +44,6 @@ If you want to jump straight in, a number of sample applications are available:
 |===
 | Sample | Build system | Description
 
-| {samples}/rest-notes-grails[Grails]
-| Gradle
-| Demonstrates the use of Spring REST docs with https://grails.org[Grails] and
-  https://github.com/spockframework/spock[Spock].
-
 | {samples}/rest-assured[REST Assured]
 | Gradle
 | Demonstrates the use of Spring REST Docs with http://rest-assured.io[REST Assured].