Fixed async example - Githubissues

I die

Fixes # Incorrect Async example

Description

Changed the documentation for the Async example on the projects home page, it was using a incorrect import.

Please select relevant options.

[x] My code follows the contribution guidelines of this project
[x] I have performed a self-review of my own code
[x] I have commented my code, particularly in hard-to-understand areas
[x] My changes generate no new warnings
[x] I formatted the code with cargo fmt
[x] I linted my code using cargo clippy and reports no warnings
[x] I have added tests that prove my fix is effective or that my feature works
[x] I have introduced no C-bindings
[x] I increased or maintained the code coverage for the project, compared to the previous commit

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