[BUG] S3E4: IMD_Sample_Clean.csv instead of .xlsx in solution

[rafaelcsv]

Where is the issue?

• Session: Session 3
• Exercise / file: S3E4.html
• Section / line Show solution — only after trying yourself!

What did you expect to happen?
The solution provided saves the clean data in .csv, when the Exercise summary text and the follwing session's solution both mention a .xlsx file.

Proposed fix
Replace this line:
export(imd_cleaning, here("data", "clean" ,"IMD_Sample_Clean.csv"))
with:
export(imd_cleaning, here("data", "clean" ,"IMD_Sample_Clean.xlsx"))