Fix multipart/form-data codegen missing --form flag for file fields

[dashrathky01]

This pull request updates the handling and testing of multipart/form-data fields in the Postman CLI code generation logic. The main focus is on improving how file fields are represented in generated CLI snippets and ensuring that both text and file fields are correctly converted.

Multipart/form-data handling improvements:

• Updated addFormDataBody in codegens/postman-cli/lib/index.js to generate CLI snippets using the correct --form flag format for file uploads, removing unnecessary inner double quotes around file paths.

Testing enhancements:

• Modified existing tests in codegens/postman-cli/test/unit/convert.test.js to expect the new --form flag format and verify the absence of inner double quotes for file paths.
• Added a new test to ensure that each field (both text and file) in a multipart/form-data request is represented with its own --form flag, and that file paths are formatted correctly without extra quotes.