Update FlagBox.js

[surajprgupta]

Fixing FlagBox defaultProps for React 18

Description

React 18 issue
after installing with npm install --force

was getting an error in the browser console
Warning: FlagBox: Support for defaultProps will be removed from function components in a future major release. Use JavaScript default parameters instead.
at FlagBox (webpack-internal:///(app-pages-browser)/./node_modules/react-intl-tel-input/dist/components/FlagBox.js:13:25)

to fix this I have removed the defaultProps and adjusted the function arguments.

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• I have used ESLint & Prettier to follow the code style of this project.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• All new and existing tests passed.