TableCell not accepting className properly

[oof2win2]

• The issue is present in the latest release.
• I have searched the issues of this repository and believe that this is not a duplicate.

Current Behavior 😯

TableCell is not correctly accepting className, as it is not applying the CSS given there properly.

Expected Behavior 🤔

TableCell should apply className correctly and apply the CSS from there, such as font-family correctly.

Steps to Reproduce 🕹

Steps:

1. Create a table with Table, TableHead, TableBody and place in some data using TableCell
2. Add a className property to the TableCell in attempt to style it
3. Apply the same CSS through the style prop
4. Observe that the className method is not working, but the style prop is.
   Example is here

Context 🔦

I am trying to create a table and style the table cells. This is not working for some reason, the styles seem to be being overridden from the base TableCell class.

Your Environment 🌎

`npx @mui/envinfo`

Used Chrome, Firefox
  System:
    OS: macOS 11.4
  Binaries:
    Node: 16.6.2 - ~/.nvm/versions/node/v16.6.2/bin/node
    Yarn: 1.22.10 - /usr/local/bin/yarn
    npm: 7.20.3 - ~/.nvm/versions/node/v16.6.2/bin/npm
  Browsers:
    Chrome: 94.0.4606.81
    Edge: Not Found
    Firefox: 93.0
    Safari: 14.1.1
  npmPackages:
    @emotion/react: ^11.4.1 => 11.4.1 
    @emotion/styled: ^11.3.0 => 11.3.0 
    @mui/core:  5.0.0-alpha.50 
    @mui/material: ^5.0.3 => 5.0.3 
    @mui/private-theming:  5.0.1 
    @mui/styled-engine:  5.0.1 
    @mui/styles: ^5.0.1 => 5.0.1 
    @mui/system:  5.0.3 
    @mui/types:  7.0.0 
    @mui/utils:  5.0.1 
    @types/react: ^17.0.27 => 17.0.27 
    react: ^17.0.2 => 17.0.2 
    react-dom: ^17.0.2 => 17.0.2 
    typescript: ^4.4.3 => 4.4.3 

[oof2win2]

Nevermind, fixed it. #28907 helped.