[docs] [TableCell] Inconsistency regarding padding and size properties

[the-question]

• This is not a v0.x issue.
• I have searched the issues of this repository and believe that this is not a duplicate.

I believe this is linked to #14561 though, but as it's already merged, I think it needs a new issue.

Expected Behavior 🤔

The description for the size property should be:

Specify the size of the cell. By default, the Table parent component set the value (medium).

The description for the CSS class sizeSmall should be:

Styles applied to the root element if size="small".

Current Behavior 😯

For the size property, the description is:

Specify the size of the cell. By default, the Table parent component set the value (normal).

For the CSS class sizeSmall, the description is:

Styles applied to the root element if padding="dense".

Steps to Reproduce 🕹

Link: TableCell's doc

1. In Props, look for size property's description
2. In CSS, look for sizeSmall class' description

Context 🔦

I was following the v3 to v4 migration guide, part about Table/TableCell and went to the TableCell's doc.

Your Environment 🌎

Tech	Version
Material-UI	v4.1.3
React	v16.8.6
Browser	Firefox 67.0.4

Edit: Modified issue to use Bug report template, even if it's not really a bug, nor a feature request, but more a doc improvement suggestion.

[oliviertassinari]

@the-question You gonna need to be explicit. I don't understand what you are trying to communicate. Please use our issue template, otherwise, you take the risk to be ignored. Thank you!

[the-question]

@oliviertassinari Thank you for the advice.
If it is indeed the doc that should be updated, I think the only needed change is in the TableCell PropTypes comments.
If you confirm and want me to create a PR with the 2 changes described in the Expected Behavior, I can do it.

[oliviertassinari]

@the-question Thanks for taking the time to follow our template. I agree, I think that the descriptions should be updated as sugested :).