Address comments.

Author: shunping

buildSrc/build.gradle.kts

@@ -52,12 +52,10 @@ plugins {
 
 // Define the set of repositories required to fetch and enable plugins.
 repositories {
-  if (isMavenAccessible) {
-    maven { url = uri("https://plugins.gradle.org/m2/") }
-  } else {
+  if (!isMavenAccessible) {
     maven { url = uri(mavenCentralMirrorUrl) }
-    maven { url = uri("https://plugins.gradle.org/m2/") }
   }
+  maven { url = uri("https://plugins.gradle.org/m2/") }
   maven {
     url = uri("https://repo.spring.io/plugins-release/")
     content { includeGroup("io.spring.gradle") }

buildSrc/src/main/groovy/org/apache/beam/gradle/Repositories.groovy

@@ -104,10 +104,10 @@ class Repositories {
         mavenLocal()
         if (checkMavenCentral()) {
           mavenCentral()
-          maven { url "https://plugins.gradle.org/m2/" }
         } else {
           maven { url "https://maven-central.storage-download.googleapis.com/maven2/" }
         }
+        maven { url "https://plugins.gradle.org/m2/" }
         maven { url "https://repo.spring.io/plugins-release" }
         maven { url "https://packages.confluent.io/maven/" }
         maven { url project.offlineRepositoryRoot }

settings.gradle.kts

@@ -38,12 +38,10 @@ pluginManagement {
     }
 
     repositories {
-        if (isMavenAccessible) {
-            gradlePluginPortal()
-        } else {
+        if (!isMavenAccessible) {
             maven { url = uri(mavenCentralMirrorUrl) }
-            gradlePluginPortal()
         }
+        gradlePluginPortal()
     }
     plugins {
         id("org.javacc.javacc") version "4.0.3" // enable the JavaCC parser generator