I have updated my com.google.gms:google-services from 3.1.1 to 3.2.0 and a warning stopped appearing.
Please find below code for your reference :
// NOTE: Do not place the application dependencies here; they belong
// in a individual module build.gradle files
I encounter same problem without using com.google.gms:google-services. A solution solving this kind problem is as follows:
1. Please check your build.gradle files of all projects and modules. Or you can just global search with key word 'compile' to find where is a cause of this warning.
2. If above method is unable to solve your warning, then use a CLI Command, ./gradlew assembleDebug -d > gradle.log
need to print detail debug information to the file named gradle.log or any else, as a information is too much. Then search the word "WARNING" to find a position in a gradle.log, usually by this way you can find what dependence or plugin causing the warning.