Update documentation for "keytool -genkey -v -keystore" from JKS to PKCS12

[tdkehoe]

Steps to Reproduce

The documentation Build and release an Android app says to create an upload keystore from the CLI:

keytool -genkey -v -keystore ~/upload-keystore.jks -keyalg RSA -keysize 2048 -validity 10000 -alias upload

This command prompts a warning

The JKS keystore uses a proprietary format. It is recommended to migrate to PKCS12 which is an industry standard format using "keytool -importkeystore -srckeystore /Users/TDK/upload-keystore.jks -destkeystore /Users/TDK/upload-keystore.jks -deststoretype pkcs12".

Perhaps the documentation should be changed to suggest using the latter command?