Fix Material-UI inline checkboxes (rjsf-team#2038)

Author: adam-beck

packages/material-ui/src/CheckboxesWidget/CheckboxesWidget.tsx

@@ -60,7 +60,7 @@ const CheckboxesWidget = ({
  <FormLabel required={required} htmlFor={id}>
  {label || schema.title}
  </FormLabel>
- <FormGroup>
+ <FormGroup row={!!inline}>
  {(enumOptions as any).map((option: any, index: number) => {
  const checked = value.indexOf(option.value) !== -1;
  const itemDisabled =
@@ -76,13 +76,7 @@ const CheckboxesWidget = ({
  onFocus={_onFocus}
  />
  );
- return inline ? (
- <FormControlLabel
- control={checkbox}
- key={index}
- label={option.label}
- />
- ) : (
+ return (
  <FormControlLabel
  control={checkbox}
  key={index}