Fix Apache snapshot repo usage (#33370)

* limit Apache snapshot repo content type

* move up Confluent repo
diff --git a/buildSrc/src/main/groovy/org/apache/beam/gradle/Repositories.groovy b/buildSrc/src/main/groovy/org/apache/beam/gradle/Repositories.groovy
index 52cbbd1..58ec64a 100644
--- a/buildSrc/src/main/groovy/org/apache/beam/gradle/Repositories.groovy
+++ b/buildSrc/src/main/groovy/org/apache/beam/gradle/Repositories.groovy
@@ -39,20 +39,25 @@
       mavenCentral()
       mavenLocal()
 
-      // Release staging repository
-      maven { url "https://oss.sonatype.org/content/repositories/staging/" }
-
-      // Apache nightly snapshots
-      maven { url "https://repository.apache.org/snapshots" }
-
-      // Apache release snapshots
-      maven { url "https://repository.apache.org/content/repositories/releases" }
-
       // For Confluent Kafka dependencies
       maven {
         url "https://packages.confluent.io/maven/"
         content { includeGroup "io.confluent" }
       }
+
+      // Release staging repository
+      maven { url "https://oss.sonatype.org/content/repositories/staging/" }
+
+      // Apache nightly snapshots
+      maven {
+        url "https://repository.apache.org/snapshots"
+        mavenContent {
+          snapshotsOnly()
+        }
+      }
+
+      // Apache release snapshots
+      maven { url "https://repository.apache.org/content/repositories/releases" }
     }
 
     // Apply a plugin which provides the 'updateOfflineRepository' task that creates an offline