Small typo in jackknife description (closed->close)

[pidefrem]

Is your documentation request related to a problem? Please describe. Just fixing a small typo in the documentation https://mapie.readthedocs.io/en/latest/theoretical_description_regression.html#the-jackknife-method

Describe the solution you'd like Replace "closed" by "close" in the following paragraph:

• original: "This method avoids the overfitting problem but can lose its predictive cover when \hat{\mu} becomes unstable, for example when the sample size is closed to the number of features (as seen in the “Reproducing the simulations from Foygel-Barber et al. (2020)” example)."
• fixed: "This method avoids the overfitting problem but can lose its predictive cover when \hat{\mu} becomes unstable, for example when the sample size is close to the number of features (as seen in the “Reproducing the simulations from Foygel-Barber et al. (2020)” example)."

[isaiahthedev]

@pidefrem @LacombeLouis Hi, can I be assigned to this? I corrected the mistake and noticed some other spelling errors on that particular file which I also corrected.