fix: delete request content-type header

[iresharma]

Summary of change

Problem Statement

Fix an issue with the Dashboard where DELETE requests get the application/json header added. This results in some frameworks rejecting requests because of a missing body

Summary of solution

(Overview of how the problem is solved by this PR)

Related issues

• Issue with delete user in Dashboard supertokens-node#663

Test Plan

Tested on all primary browsers for:

• Chrome
  • Desktop
  • Mobile
  • Tablet
• Safari
  • Desktop
  • Mobile
  • Tablet
• Firefox
  • Desktop
  • Mobile
  • Tablet
• (Optional) Tested on Safari 12 (Physical or emulator)
  • iPad
  • iPhone
• (Optional) Tested on physical mobile and tablet device for:
  • Android
  • iOS (including iPadOS)

Documentation changes

(If relevant, please create a PR in our docs repo, or create a checklist here highlighting the necessary changes)

Checklist for important updates

• Changelog has been updated
• Changes to the version if needed
  • In package.json
  • In package-lock.json
  • In src/version.ts
• Had run npm run build
• Had installed and ran the pre-commit hook

Remaining TODOs for this PR

• Item1
• Item2