google-services.json not found in flavor/build-type directories when using flavors with capital first letter

With 4.2.0 of the plugin the google-services.json was also searched in subdirectories flavor/build-type when the flavor starts with a capital letter. With 4.3.2 it is only searched in the lower-cased version of the flavor.

**To Reproduce**
Steps to reproduce the behavior:
1. Put google-services.json into a subdirectory `/` where `` starts with an uppercase character.
2. `./gradlew :app:processGoogleServices`

**Expected behavior**
Compile succeeds

**Screenshots**
File google-services.json is missing. The Google Services Plugin cannot function without it.
Searched Location:
/home/kurt/ [REDACTED]/app/google-services.json

**Desktop (please complete the following information):**
- Gradle version: 5.6.1
- Android Studio version: n/a
- working Plugin name and version: com.google.gms:google-services:4.2.0
- failing Plugin name and version: com.google.gms:google-services:4.3.2 (as well as 4.3.0)

**Additional context**
Description how to use flavor-specific google-services.json:
https://stackoverflow.com/questions/30772201/google-services-json-for-different-productflavors
https://android.jlelse.eu/how-to-use-different-google-services-json-file-with-multiple-product-flavors-android-7853d98dd6c0