Remove x86 from abi filters.

splits {
        abi {
            reset()
            enable true
            universalApk false
            include "armeabi-v7a", "x86"
        }
    }

Make following changes in build.gradle :

./android/app/build.gradle

Generate different APK's for different architecture

def enableSeparateBuildPerCPUArchitecture = true

Enable ProGuard :

def enableProguardInReleaseBuilds = true

Also set minifyEnabled true and shrinkResources true

buildTypes {
        release {
            minifyEnabled true
            shrinkResources true
            proguardFiles getDefaultProguardFile("proguard-android.txt"), "proguard-rules.pro"
        }
    }