Revert "Use artifactoryUsername/Password for plugin repositories"

This reverts commit 6db194da27.

build.gradle

@@ -5,15 +5,7 @@ buildscript {
 		classpath 'io.spring.nohttp:nohttp-gradle:0.0.5.RELEASE'
 	}
 	repositories {
-		maven {
-			url = 'https://repo.spring.io/plugins-snapshot'
-			if (project.hasProperty('artifactoryUsername')) {
-				credentials {
-					username "$artifactoryUsername"
-					password "$artifactoryPassword"
-				}
-			}
-		}
+		maven { url 'https://repo.spring.io/plugins-snapshot' }
 		maven { url 'https://plugins.gradle.org/m2/' }
 	}
 }