rm jcenter() and replace with mavenCentral()

jcenter() is no longer getting updates and will be shut down soon.
Simplified maven { url 'https://maven.google.com' } into google().
Simplified maven { url 'https://plugins.gradle.org/m2/' } into
gradlePluginPortal().
Gradle 7 requires all URLs to be HTTPS, updated Huawei.

Author: jkasten2

OneSignalSDK/build.gradle

@@ -18,16 +18,16 @@ buildscript {
 
     repositories {
         google()
-        jcenter()
-        maven { url 'https://maven.google.com' }
+        mavenCentral()
 
         // OneSignal-Gradle-Plugin - Local testing
         // maven { url uri('../../repo') }
 
         // OneSignal-Gradle-Plugin - Public version
-        maven { url 'https://plugins.gradle.org/m2/' }
+        gradlePluginPortal()
+
         // Huawei maven
-        maven { url 'http://developer.huawei.com/repo/' }
+        maven { url 'https://developer.huawei.com/repo/' }
     }
     dependencies {
         classpath "com.android.tools.build:gradle:$androidGradlePluginVersion"
@@ -46,12 +46,11 @@ buildscript {
 allprojects {
     repositories {
         google()
-        jcenter()
+        mavenCentral()
         flatDir {
             dirs 'libs'
         }
-        maven { url 'https://maven.google.com' }
         // Huawei maven
-        maven { url 'http://developer.huawei.com/repo/' }
+        maven { url 'https://developer.huawei.com/repo/' }
     }
-}
+}