Remove android.enableJetifier line from gradle.properties & Remove jetifier pacakge and jetify usage

[emanuelb]

edge-react-gui/android/gradle.properties

Lines 24 to 25 in 19ca133

	# Automatically convert third-party libraries to use AndroidX
	android.enableJetifier=true

see this guide for the steps to ensure it's safe to remove above lines (check that all deps are already fully migrated to AndroidX)
https://medium.com/dipien/say-bye-bye-to-android-jetifier-a7e0d388f5d6

The jetifier package exists in package.json

edge-react-gui/package.json

Line 220 in 9d93d01

"jetifier": "^1.6.5",

And npx jetify call in ./postinstall.sh:

edge-react-gui/postinstall.sh

Lines 19 to 20 in 57c7801

	# Fix Android dependencies:
	npx jetify

Both can be removed if project+deps fully migrated to AndroidX, also from https://www.npmjs.com/package/jetifier

Note that jetifier is included and ran automatically with react-native-community/cli for React Native versions 0.60 and above, so you do not need to install and run jetifier manually.