Update installation.rst - fix typos

[pbadeer]

Thank you for contributing to Salesman, before you continue make sure that:

• Tests still pass: poetry run pytest
• There are no lint errors: poetry run pre-commit run --all-files

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 98.17%. Comparing base (8105e84) to head (dc10642). Report is 4 commits behind head on master.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #36 +/- ## ======================================= Coverage 98.17% 98.17% ======================================= Files 49 49 Lines 2032 2032 ======================================= Hits 1995 1995 Misses 37 37 ```

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.

[dinoperovic]

Thanks @pbadeer, adding you to credits :)