Update validate-release.md with non-interactive mode

[imbajin]

use echo -e "5\ny\n" | gpg --batch --command-fd 0 --edit-key $USER trust to avoid interactive mode

for more than one:

for key in $(gpg --no-tty --list-keys --with-colons | awk -F: '/^pub/ {print $5}'); do
  echo -e "5\ny\n" | gpg --batch --command-fd 0 --edit-key "$key" trust
done