Spawned processes aren't killed

**Describe the bug**
When launching processes via `:`, they don't seem to fully exit/terminate.

**To Reproduce**
1. Start lazygit
2. `:`
3. echo "cat"
4. `:`
5. ` Enter`
6. `q`
7. `ps aux | grep echo`
8. See multiple unterminated processes

**Expected behavior**
Processes to exit when completed

**Screenshots**

**Version info:**
commit=, build date=, build source=homebrew, version=0.44.1, os=darwin, arch=arm64, git version=2.46.1
git version 2.46.1

**Additional context**
Add any other context about the problem here.

**Note:** please try updating to the latest version or [manually building](https://github.com/jesseduffield/lazygit/#manual) the latest `master` to see if the issue still occurs.