updated content-type in main function

[codewithkushagra]

What does this PR do?

This PR is a bug fix for the issue #220, which resolves the issue of python chatgpt template not being rendered.

Test Plan

• The issue was the we were send Content-Type from backend in python from appwrite function. Which was not interpreated by browser correctly.
• I verified the above problem by going to inspect elements in google chrome and checking the content-type was showing plain/text, which was creating problem of HTML page not being rendered.
• To fix the issue, I corrected the Content-Type changing the spelling to content-type, now the browser was able to detect the content-type correctly.
• I have tested this by creating a cloud instance of prompt chatgpt using appwrite cloud, and then changing code in my own instance.
• I have deployed 2 instance
  - The original version with is - https://652040168d5644809a5a.appwrite.global/
  - The corrected version is - https://651f1233b7aa4fe187ae.appwrite.global/

Related PRs and Issues

The related issue is #220

Have you read the Contributing Guidelines on issues?

Yes, I have read the contributing guidelines on issues.