Remove artifactory plugin from build

As we're moving the build to Concourse CI, we don't need to use the
Artifactory plugin anymore. Our build will publish the artifacts to a
repository on the local filesystem and will push its content to
Artifactory with the spring-io/artifactory-resource.

This commit also adds the conditional configuration for publishing to a
local repository.

See gh-22490

build.gradle

@@ -7,7 +7,6 @@ plugins {
 	id 'io.spring.nohttp' version '0.0.4.RELEASE'
 	id 'de.undercouch.download' version '4.0.0'
 	id 'com.gradle.build-scan' version '3.2'
-	id "com.jfrog.artifactory" version '4.12.0' apply false
 	id "io.freefair.aspectj" version '4.1.1' apply false
 	id "com.github.ben-manes.versions" version '0.24.0'
 }

gradle/publications.gradle

@@ -1,5 +1,4 @@
 apply plugin: "maven-publish"
-apply plugin: 'com.jfrog.artifactory'
 
 publishing {
 	publications {
@@ -50,6 +49,16 @@ publishing {
 	}
 }
 
-artifactoryPublish {
-	publications(publishing.publications.mavenJava)
+configureDeploymentRepository(project)
+
+void configureDeploymentRepository(Project project) {
+	project.plugins.withType(MavenPublishPlugin.class).all {
+		PublishingExtension publishing = project.getExtensions().getByType(PublishingExtension.class);
+		if (project.hasProperty("deploymentRepository")) {
+			publishing.repositories.maven {
+				it.url = project.property("deploymentRepository")
+				it.name = "deployment"
+			}
+		}
+	}
 }