[EXTERNAL] fix(box_recursion): fix expected code

[sadiqui]

1. Make it clear, that student should complete this type alias, guided by instructions:

Additionally, create a type named Link, which will be the connection between the WorkEnvironment and Worker structures. It will point to None if there is no Worker to point to.

- pub type Link;
+ pub type Link = _; // Complete type alias

2. role field of Worker structure, is expected to be of type Role. Tests Need It as checks expect "Role::CEO, not "CEO".

- pub role: String,
+ pub role: Role,

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Related files:

• Tests: https://github.com/01-edu/rust-tests/blob/master/tests/box_recursion_test/src/lib.rs
• Solution: https://github.com/01-edu/rust-tests/blob/master/solutions/box_recursion/src/lib.rs

[pedrodesu]

Looks good to me! A small refactor I missed on the markdown. Thank you @sadiqui