Add interval notation for include_boundaries parameter for the function check_scalar

Describe the issue linked to the documentation

This is the current documentation for parameter include_boundaries in the function check_scalar:

“left”: only min_val is included in the valid interval;

“right”: only max_val is included in the valid interval;

“both”: min_val and max_val are included in the valid interval;

“neither”: neither min_val nor max_val are included in the valid interval.

Suggest a potential alternative/fix

Add the following interval notation in the documentation for the function check_scalar:

• “left” [ , )
• “right” ( , ]
• “both” [ , ]
• “neither” ( , )

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[glemaitre]

@reshamas @thomasjpfan I think that we can keep the English notation. I hope this is mainly what we used up to now. Since parentheses do not exist in French but that we deal with interval, I think that people will be able to find out.

[yadav-sachin]

@reshamas @thomasjpfan I went ahead and added the English interval notation in the pull request (as I think this notation is more widely used). If the French interval notation is preferred, I will change it accordingly.