Fixed: Fix broken bootstrap zips by adding termux-keyring dependency

The science-repo and game-repo were recently removed and their packages were added to the main repo.
During this their dependencies were removed from bootstrap zips in generate-bootstrap.sh script.
However, both these packages were dependent on termux-keyring package and the script did not have an entry itself for termux-keyring, so their removal resulted in missing termux-keyring package in bootstrap, which resulted in no keys to exist in `$TERMUX_PREFIX/etc/apt/trusted.gpg.d/` on fresh install, which resulted in `The following signatures couldn't be verified because the public key is not available: NO_PUBKEY*` errors when running `apt update` command for any bootstrap generated after Dec 14, 2021.

https://github.com/termux/termux-packages/commits/master/scripts/generate-bootstraps.sh
87b9cd3cf
758ec3a92

a3307822
f8746124

scripts/generate-bootstraps.sh

@@ -325,6 +325,7 @@ for package_arch in "${TERMUX_ARCHITECTURES[@]}"; do
 	pull_package sed
 	pull_package tar
 	pull_package termux-exec
+	pull_package termux-keyring
 	pull_package termux-tools
 	pull_package util-linux
 	pull_package xz-utils