[data grid] GridToolbar filter 'is any of' selection is showing outlined input instead of regular input

[tdcaot]

Steps to reproduce

Anywhere where have the Datagrid filter, is any of selection.
Link to live example: https://mui.com/x/react-data-grid/filtering/multi-filters/

Steps:

1. Access DataGrid(Free edition)
2. Open FILTER menu
3. Select 'is any of' in Operator(the value input field is become the outlined)
   
   

Current behavior

FILTER > 'is any of' Operator(the value input field is become the outlined)

Expected behavior

Regular variant displayed just like another Operator selection

Context

No response

Your environment

npx @mui/envinfo

  System:
    OS: Windows 11 10.0.22631
  Binaries:
    Node: 21.7.3 - C:\Program Files\nodejs\node.EXE
    npm: 10.5.2 - C:\Program Files\nodejs\npm.CMD
    pnpm: Not Found
  Browsers:
    Chrome: Not Found
    Edge: Chromium (123.0.2420.97)
  npmPackages:
    @emotion/react: ^11.11.4 => 11.11.4
    @emotion/styled: ^11.11.5 => 11.11.5
    @mui/base:  5.0.0-beta.40
    @mui/core-downloads-tracker:  5.15.17
    @mui/icons-material: ^5.15.17 => 5.15.17
    @mui/material: ^5.15.17 => 5.15.17
    @mui/private-theming:  5.15.14
    @mui/styled-engine:  5.15.14
    @mui/system: ^5.15.15 => 5.15.15
    @mui/types:  7.2.14
    @mui/utils:  5.15.14
    @mui/x-data-grid: ^7.3.2 => 7.3.2
    @mui/x-date-pickers: ^7.3.2 => 7.3.2
    @types/react: ^18 => 18.3.1
    react: ^18 => 18.3.1
    react-dom: ^18 => 18.3.1
    typescript: ^5 => 5.4.5

Search keywords: GridToolbar, is any of, filter

[michelengelen]

Hey @tdcaot
thanks for raising this.
It's a relatively easy fix, so I'll add the gfi label.
here is a diff to get it started:

diff --git a/packages/x-data-grid/src/components/panel/filterPanel/GridFilterInputMultipleValue.tsx b/packages/x-data-grid/src/components/panel/filterPanel/GridFilterInputMultipleValue.tsx
index eb8bac5c6..ffa56e4b4 100644
--- a/packages/x-data-grid/src/components/panel/filterPanel/GridFilterInputMultipleValue.tsx
+++ b/packages/x-data-grid/src/components/panel/filterPanel/GridFilterInputMultipleValue.tsx
@@ -21,7 +21,7 @@ function GridFilterInputMultipleValue(props: GridFilterInputMultipleValueProps)
     error,
     helperText,
     size,
-    variant,
+    variant = 'standard',
     ...other
   } = props;
   const TextFieldProps = {