Plugin project :firebase_core_web not found. Please update settings.gradle

//Upgrade minSdk in app/build.gradle to 23.

android {
    // ...
    defaultConfig {
        // ...
        minSdkVersion 23
    }
}

// Update settings.gradle to contain the following

include ':app'

def flutterProjectRoot = rootProject.projectDir.parentFile.toPath()

def plugins = new Properties()
def pluginsFile = new File(flutterProjectRoot.toFile(), '.flutter-plugins')
if (pluginsFile.exists()) {
    pluginsFile.withReader('UTF-8') { reader -> plugins.load(reader) }
}

plugins.each { name, path ->
    def pluginDirectory = flutterProjectRoot.resolve(path).resolve('android').toFile()
    include ":$name"
    project(":$name").projectDir = pluginDirectory
}