"Commit changes using git editor" does not respect "os.editCommand"

**Describe the bug**

The `Commit changes using git editor` functionnality does not respect what the user specified in the configuration file under `os.editCommand` (or `os.openCommand`)

**To Reproduce**
Steps to reproduce the behavior:
1. Create a configuration file where `os.editCmd` is different that `git config core.editor`
2. Open `lazygit`
3. Hit `C`
4. Observe

**Expected behavior**

Lazygit should respect the user option first, as specified in the documentation.

**Desktop (please complete the following information):**
- OS: Linux
- The last commit id if you built project from sources (built using `go install`)