Fix minor error in 'var' example

[g3rwy]

Var example fix

Only changed one line in builtin 'var' example string, it should show 2 instead of a when print var 'a is performed. No other changes has been made

Type of change

• [ ] Code cleanup
• [ ] Unit tests (added or updated unit-tests)
• [ ] Bug fix (non-breaking change which fixes an issue)
• [ ] Enhancement (implementation update, or general performance enhancements)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [x] Documentation (documentation-related additions)

[drkameleon]

Apparently, there seems to be a Windows-related error (I have seen once sth similar, but I cannot honestly say what is going on here, since the master branch has been compiling fine up to now...)

So, let's put this on hold, until this is solved: https://github.com/arturo-lang/arturo/issues/1630

[drkameleon]

Ready to merge! 🚀