[7_heavy_tails]_add_.

[shlff]

Good afternoon, @jstac , this PR adds . at the ends of following sentences in lecture heavy_tails:

• For example, it fails for the Cauchy distribution
• `which we solve for :math:\muand :math:\sigmagiven :math:\alpha = 1.05```

[github-actions[bot]]

🚀 Deployed on https://5fe959f5ee5a2ff9f9f7a49b--practical-lalande-b89631.netlify.app

[jstac]

Thanks @shlff