Upgrade build tools and switch from jcenter() to mavenCentral()

Use of mavenCentral() is now the default when making a new project
in Android Studio. Furthermore, Android Studio displays warnings
when jcenter() is used.

PiperOrigin-RevId: 377268744

build.gradle

@@ -14,17 +14,17 @@
 buildscript {
     repositories {
         google()
-        jcenter()
+        mavenCentral()
     }
     dependencies {
-        classpath 'com.android.tools.build:gradle:4.0.1'
-        classpath 'com.google.android.gms:strict-version-matcher-plugin:1.2.1'
+        classpath 'com.android.tools.build:gradle:4.2.1'
+        classpath 'com.google.android.gms:strict-version-matcher-plugin:1.2.2'
     }
 }
 allprojects {
     repositories {
         google()
-        jcenter()
+        mavenCentral()
     }
     if (it.hasProperty('externalBuildDir')) {
         if (!new File(externalBuildDir).isAbsolute()) {