Flutter Integration with Firebase Build Gradle Error

I am trying to integrate my application developed on Flutter with Firebase, however while following the tutorial, I’m facing some issues.

Copying exact thing from Firebase documentation:

dependencies {
    classpath 'com.android.tools.build:gradle:7.2.0'
    classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
    id("com.google.gms.google-services:4.3.15") version "4.3.15" apply false
}

Updating them with some solutions found:

dependencies {
    classpath 'com.android.tools.build:gradle:7.2.0'
    classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
    classpath 'com.google.gms.google-services:4.3.15'
}

I’m still facing the issue in Build. I have also checked the google-services.json file which is in app folder and the build gradle inside it looks like:

apply plugin: 'com.android.application'
apply plugin: 'kotlin-android'
apply plugin: 'com.google.gms.google-services'
apply from: "$flutterRoot/packages/flutter_tools/gradle/flutter.gradle"


dependencies {
    implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk7:$kotlin_version"
    implementation(platform("com.google.firebase:firebase-bom:32.1.1"))
}