Remove --features jsonrpc from scripts/ndk-make.sh

[link2xt]

This is a breaking change introduced in the recent core: deltachat/deltachat-core-rust#6417
This currently prevents building nightlies because ndk-make script fails with error: the package 'deltachat_ffi' does not contain this feature: jsonrpc.
The core with this change is not released yet as I want to test the new group consistency a bit before tagging it, but I guess it is possible to update to the latest main already and adjust the build process so nightlies can be built.