[BUG] Cant disable HSTS on existing Proxy

[Roalkege]

Describe the bug
I want to disable HSTS on an existing HTTP Proxy

To Reproduce

1. Go to HTTP Proxy
2. Select a Proxy with HSTS enabled and click "Edit proxy rules"
3. Click Custom Headers
4. Navigate to security headers.
5. Deactivate the slider
6. Scroll down and click save and after that close
7. Click save
8. Reproduce 2-4 and HSTS is still enabled

Expected behavior
HSTS should be disabled for the proxy

Browser (if it is a bug appears on the UI section of the system):

• OS: Windows 11
• Browser: Chrome
• Version: 131.0.6778.109

Host Environment (please complete the following information):

• Arch: x64
• Device: Custom Build
• OS: Unraid
• Version 7.0.0-rc.1
• Docker Version: v.3.1.4

[tobychui]

I can reproduce this, but what is weird is that the code that powers this feature never changed since this was introduced.
Will look into it this weekend.