visudo-rs: Improve the error message

[sylvestre]

$ visudo-rs                                                                                                                                         
Come on... you can do better than that.

syntax error: expected parameter
syntax error: expected host name

What now? e(x)it without saving / (e)dit again:

"Come on... you can do better than that." is too informal

[codecov[bot]]

Codecov Report

Patch coverage has no change and project coverage change: +0.01% :tada:

Comparison is base (fbfbabd) 55.24% compared to head (84c00d1) 55.25%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #767 +/- ## ========================================== + Coverage 55.24% 55.25% +0.01% ========================================== Files 72 72 Lines 9840 9840 ========================================== + Hits 5436 5437 +1 + Misses 4404 4403 -1 ``` | [Files Changed](https://app.codecov.io/gh/memorysafety/sudo-rs/pull/767?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=memorysafety) | Coverage Δ | | |---|---|---| | [src/visudo/mod.rs](https://app.codecov.io/gh/memorysafety/sudo-rs/pull/767?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=memorysafety#diff-c3JjL3Zpc3Vkby9tb2QucnM=) | `0.00% <0.00%> (ø)` | | ... and [1 file with indirect coverage changes](https://app.codecov.io/gh/memorysafety/sudo-rs/pull/767/indirect-changes?src=pr&el=tree-more&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=memorysafety)

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[pvdrz]

I did this jokingly and absolutely forgot about it :sweat_smile:

[sylvestre]

@pvdrz no worries, I knew you could do better than this ;)

[pvdrz]

🤣