Keep dependency repository definitions well defined

hibernate-core/hibernate-core.gradle

@@ -10,10 +10,6 @@ plugins {
     id 'org.hibernate.build.xjc-jakarta'
 }
 
-repositories {
-    gradlePluginPortal()
-}
-
 description = 'Hibernate\'s core ORM functionality'
 
 apply from: rootProject.file( 'gradle/published-java-module.gradle' )

settings.gradle

@@ -30,13 +30,15 @@ dependencyResolutionManagement {
             url( rootProject.property( "mavenMirror" ) )
         }
         mavenCentral()
-        // Needed for the RC versions of Jakarta Persistence
-        maven {
-            url "https://jakarta.oss.sonatype.org/content/repositories/releases/"
-        }
-        // Needed for the SNAPSHOT versions of Jakarta Persistence
-        maven {
-            url "https://jakarta.oss.sonatype.org/content/repositories/snapshots/"
+        if (System.env['JPA_PREVIEW'] != null) {
+            // Needed for the RC versions of Jakarta Persistence
+            maven {
+                url "https://jakarta.oss.sonatype.org/content/repositories/releases/"
+            }
+            // Needed for the SNAPSHOT versions of Jakarta Persistence
+            maven {
+                url "https://jakarta.oss.sonatype.org/content/repositories/snapshots/"
+            }
         }
 
         //Allow loading additional dependencies from a local path;