[TextField] Fix label notch for custom htmlFontSize (#19558)

Author: kusmierz

packages/material-ui/src/InputBase/InputBase.js

@@ -39,9 +39,8 @@ export const styles = theme => {
     /* Styles applied to the root element. */
     root: {
       // Mimics the default input display property used by browsers for an input.
-      fontFamily: theme.typography.fontFamily,
+      ...theme.typography.body1,
       color: theme.palette.text.primary,
-      fontSize: theme.typography.pxToRem(16),
       lineHeight: '1.1875em', // Reset (19px), match the native input line-height
       boxSizing: 'border-box', // Prevent padding issue with fullWidth.
       position: 'relative',