Column labels are being converted into upper case

Column labels are being converted to upper case. It is very random, though. Some label are not being converted.
```
const columns = [
{
name: 'id',
label: 'Id',
options: {
display: false,
filter: true,
sort: true,
},
},

{
name: 'photo',
label: 'Photo',
options: {
filter: false,
sort: true,
customBodyRender: (value) => ,
},
},
{
name: 'studentName',
label: 'Student',
options: {
filter: true,
sort: true,
},
},
{
name: 'phone',
label: 'Phone',
options: {
filter: true,
sort: true,
},
},

{
name: 'course',
label: 'COURSE',
options: {
filter: false,
sort: false,
},
},
{
name: 'enrolledOn',
label: 'Admission Date',
options: {
filter: false,
sort: true,
},
},
{
name: 'paidFees',
label: 'Paid Fees',
options: {
filter: true,
sort: true,
},
},
{
name: 'dueFees',
label: 'Due Fees',
options: {
filter: true,
sort: false,
},
},
];

```
[Image](https://i.postimg.cc/GhmnTggQ/Screenshot-2022-06-07-at-5-03-54-PM.png)

## Your Environment

| Tech | Version |
|--------------|---------|
| Material-UI | 5.5.3 |
| MUI-datatables | 4.2.2 |
| React | ^18.0.0 |

Start by reproducing the issue with the supplied columns example in the reported Material-UI 5.5.3, MUI-datatables 4.2.2, and React 18 environment, then trace how column labels are rendered. Done means labels such as “Id”, “Photo”, “Student”, and “Admission Date” consistently retain their configured casing rather than being converted to uppercase.

Written by the indexing model from the issue text.