Update tuistenv when running tuist update

[pepicrft]

Resolves #260

Short description 📝

With this change, running tuist update also updates tuistenv.

[codecov]

Codecov Report

Merging #288 into master will increase coverage by 0.12%.
The diff coverage is 98.46%.

@@            Coverage Diff             @@
##           master     #288      +/-   ##
==========================================
+ Coverage    87.9%   88.02%   +0.12%     
==========================================
  Files         268      271       +3     
  Lines        9419     9480      +61     
==========================================
+ Hits         8280     8345      +65     
+ Misses       1139     1135       -4

Impacted Files	Coverage Δ
...uistEnvKitTests/Updater/Mocks/MockEnvUpdater.swift	100% <100%> (ø)
...urces/TuistCoreTesting/Utils/MockFileHandler.swift	84% <100%> (+8%)	⬆️
...sts/TuistEnvKitTests/Updater/EnvUpdaterTests.swift	100% <100%> (ø)
Sources/TuistCore/Utils/System.swift	56.6% <100%> (+0.83%)	⬆️
Tests/TuistEnvKitTests/Updater/UpdaterTests.swift	100% <100%> (ø)	⬆️
Sources/TuistEnvKit/Updater/Updater.swift	100% <100%> (ø)	⬆️
Sources/TuistEnvKit/Updater/EnvUpdater.swift	95.45% <95.45%> (ø)
... and 2 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 7aaebf4...c315296. Read the comment docs.

[tuistbot]

	1 Warning
⚠️	Have you introduced any user-facing changes? If so, please take some time to update the documentation. Keeping the documentation up to date makes it easier for users to learn how to use Tuist.

Generated by 🚫 Danger