FIX: fix typos in documentation

[FaustinPulveric]

Description

In https://mapie.readthedocs.io/en/latest/theoretical_description_regression.html, section 3, there is an approximation:

The resulting confidence interval can therefore be summarized as follows

Should be:

The resulting prediction interval can therefore be summarized as follows

Similar typo in section 4.

Type of change

Please remove options that are irrelevant.

• Bug fix (non-breaking change which fixes an issue)

Checklist

• I have read the contributing guidelines
• I have updated the HISTORY.rst and AUTHORS.rst files
• Linting passes successfully: make lint
• Typing passes successfully: make type-check
• Unit tests pass successfully: make tests
• Coverage is 100%: make coverage
• When updating documentation: doc builds successfully and without warnings: make doc
• When updating documentation: code examples in doc run successfully: make doctest