Add word percent or % symbol after 50

[ddslug]

Description:

The percent symbol did not show up in the document even though it was typed in the source code.

Suggested Fix:

No response

Volume & Lab (By Name)

Data Science Essentials: Pandas1

Source Lines

Relevant segments in `/DataScienceEssentials/Pandas1/Pandas1.md`:
- Approximate line: 349:
  - Section: Problem 3:
    - List item: What year had the highest crim...:
      - TeX: $50%$ (`50%`)