Why do I get "Configuration 'compile' is obsolete"

I have read SO threads about this problem and I have added

classpath 'com.google.gms:google-services:3.2.1'

to build.gradle, but it doesnt help. here's the full gradle:

buildscript {
    repositories {
        maven {
            url 'https://maven.fabric.io/public'
        }
        mavenCentral()
        jcenter()
        google()
    }
    dependencies {
        classpath 'io.fabric.tools:gradle:1.26.1'
        classpath 'com.android.tools.build:gradle:3.2.1'
        classpath 'com.google.gms:google-services:3.2.1'
    }
}

apply plugin: 'com.android.application'
apply plugin: 'io.fabric'

repositories {
    maven { url "https://jitpack.io" }
    maven { url 'https://maven.fabric.io/public' }
    maven {
        url uri('mint-plugin-repo-5.2.4')
    }
    google()
}
android {

    flavorDimensions "default"

    signingConfigs {
        config {
            keyAlias 'xxx'
            keyPassword 'xxx'
            storeFile file('/Users/claude/Documents/xxx')
            storePassword 'xxx'
        }
    }
    compileSdkVersion 28

    defaultConfig {
        targetSdkVersion 28
        multiDexEnabled true
        vectorDrawables.useSupportLibrary = true
        minSdkVersion 19
    }

    productFlavors {
        So_TEST {

            applicationId "com.bluelionsolutions.mytaxicontrol"
            versionName "5.0.3.4"

            buildConfigField 'String', 'mtc', '"xxx"'
            resValue "string", "app_name", "xxx"

            resValue "string", "google_maps_api_key", "xxx"
        }
    }
}

dependencies {
    implementation 'com.braintreepayments.api:drop-in:3.7.0'
    implementation 'commons-codec:commons-codec:1.10'
    implementation 'com.android.support:appcompat-v7:28.0.0'
    implementation 'com.android.support:design:28.0.0'
    implementation 'com.android.support:mediarouter-v7:28.0.0'
    implementation 'com.android.support:multidex:1.0.3'
    implementation 'com.android.support:support-v4:28.0.0'
    implementation 'com.google.android.gms:play-services:11.8.0'
    implementation('com.crashlytics.sdk.android:crashlytics:2.9.5@aar') {
        transitive = true;
    }
}
apply plugin: 'com.google.gms.google-services'