https://github.com/antimatter15/tesseract-rs/issues/32#issuecomment-1310553986

4.1 was released in July 2019 (>3 years ago). So most people should have
it. Except for people using their Linux distro's provided version, it is
unlikely anyone is on such an old version.

I've not added the restriction to the windows build, as I can't test it
so easily and because I don't expect it to be a problem for Windows users.

Tested with these commands (more or less)
```bash
podman container run --rm -it -v "$(pwd)/Documents:/var/Documents:Z" linuxmintd/mint19.3-amd64

apt-get update && apt-get dist-upgrade --assume-yes
apt-get install curl libtesseract-dev tesseract-ocr-eng pkg-config clang --assume-yes

curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh
source "$HOME/.cargo/env"

cd /var/Documents/github.com/ccouzens/tesseract-sys
cargo clean
cargo test
```

It isn't actually true that tesseract-sys requires 4.1.0. But everything
that builds on top of it does. It is simplist to put the restriction
here.