[Bug]: SSL client certificate broken with 3.12.2 connection wizard

### ⚠️ Before submitting, please verify the following: ⚠️

- [X] This is a **bug**, not a question or a configuration issue.
- [X] This issue is **not** already reported on Github (I've searched it).
- [X] Nextcloud Server and Desktop Client are **up to date**. See [Server Maintenance and Release Schedule](https://github.com/nextcloud/server/wiki/Maintenance-and-Release-Schedule) and [Desktop Releases](https://nextcloud.com/install/#install-clients) for supported versions.
- [X] I agree to follow Nextcloud's [Code of Conduct](https://nextcloud.com/contribute/code-of-conduct/)

### Bug description

The Nextcloud Connection Wizard can't proceed with the account creation because it shows a 400 Bad Request error where the web server does not receive the SSL client certificate. It ist not possible to add the account.
This worked perfectly with the previous 3.9.3 client, but now with 3.12.2 it no longer works.

### Steps to reproduce

1. Add a new account (Account -> Add new)
2. Click "Log In" button
3. Add Server Address
4. Click on "Configure client-side TLS certificate"
5. Load pkcs12 client-side cert and enter cert password
6. Now appears the error
- Failed to connect to Nextcloud at https://????.com
Server replied “400 Bad Request” to GET https://????.com/status.php”
- Could not load certificate. Maybe wrong password?

### Expected behavior

It should be possible to add a new account to the client through the Nextcloud Connection Wizard which has an SSL client certificate in order connect to the Nextcloud server which requires client certificate authentication.

### Which files are affected by this bug

not files

### Operating system

Windows

### Which version of the operating system you are running.

Win 11

### Package

Other

### Nextcloud Server version

27.1.7

### Nextcloud Desktop Client version

3.12.2

### Is this bug present after an update or on a fresh install?

Fresh desktop client install

### Are you using the Nextcloud Server Encryption module?

Encryption is Disabled

### Are you using an external user-backend?

- [ ] Default internal user-backend
- [ ] LDAP/ Active Directory
- [ ] SSO - SAML
- [ ] Other

### Nextcloud Server logs

_No response_

### Additional info

_No response_