Fix a minor formatting mistake in build-unix.md

[Minor Spelling Mistake, I Win](https://github-production-user-asset-6210df.s3.amazonaws.com/96183936/284324285-d9adcb91-4aa2-4fa1-bccc-c1a9235d4109.webm)

doc/build-unix.md

@@ -67,6 +67,7 @@ Before installing the dependencies, ensure your system is updated and has the la
 ```bash
 sudo apt-get update
 sudo apt-get upgrade
+```
 
 **Required dependencies** :
 ```bash