Machan note these points
01. You are using out dateted flutter version, so update you flutter to latest version. Bcoz in new flutter version they have change this gradle plugin loading old way to new optimized way, now almost all plugins tend into migrating into new flutter build system and new version. So you first update flutter
02. What I suggest to do is,
-> First update flutter
-> Create brand new project with same package name in different folder
-> Migrate your home widget into new project alone with Google Maps keys etc. Finally add your dependencies into new yml file and use the new project
-> If needed do flutter clean > flutter pub cache clean > flutter pub cache repair -> flutter pub get