Remove spaces from docs landing page

[williambdean]

The landing page for CausalPy
has spaces in the code blocks. These should be removed for better formatting.

---

📚 Documentation preview 📚: https://causalpy--527.org.readthedocs.build/en/527/

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.19%. Comparing base (91ecda2) to head (2c3a0eb).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #527   +/-   ##
=======================================
  Coverage   95.19%   95.19%           
=======================================
  Files          28       28           
  Lines        2457     2457           
=======================================
  Hits         2339     2339           
  Misses        118      118           

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