remove extra space

[Gautzilla]

an extra space made the markdown fail displaying keys in italics:

[kotp]

Forum discussion linked here.

[BethanyG]

Thank you for this PR. 😄

In the future, if you spot a typo or spelling error in a concept exercise introduction.md, please make sure to also check for the same error in the concept introduction.md & about.md files. The text for these two concept files often overlaps the exercise introduction.md. In this case, there was only one typo -- but for many exercises, there might be up to three.

The concept about.md and introduction.md files can be found in this repo under https://github.com/exercism/python/tree/main/concepts/<concept name>/about.md and https://github.com/exercism/python/tree/main/concepts/<concept name>/introduction.md.

Thanks again for the catch!