Increase memory in gradle.properties to avoid OOM in android apk compilation

[emanuelb]

Compiling this app with Containerfile at: https://gitlab.com/walletscrutiny/walletScrutinyCom/-/issues/208

will fail with OOM error unless running the following command sed -i '/org.gradle.jvmargs/s/^#//g' gradle.properties; which used to uncomment this line: https://github.com/bitcoin-dot-org/BitcoinWalletMobile/blob/56d56d767c95a33afa4ca9da17b0ad206ecd416d/android/gradle.properties#L13

so it's better to increase the defaults to be enough for app compilation.