Delay in loading alert conditions

### Environment

SaaS (https://sentry.io/)

### Steps to Reproduce

1. Go to the Alerts page and click on "Create Alert"
2. Choose an alert type and click on "Set Conditions"

### Expected Result

The page to set the alert rule conditions loads immediately.

### Actual Result

The page appears initially grayed out, and then reloads after 10-30 seconds and becomes functional again. A 400 error with "No feature specified" message and another 400 error with "Invalid input." message appear in the network logs while the page is grayed out.

Video reproduction from my test Sentry organization:
https://github.com/user-attachments/assets/f7213831-b6ae-49d5-937d-d46ac531e708

### Product Area

Alerts

### Link

_No response_

### DSN

_No response_

### Version

_No response_

Reproduce the Alerts page flow by choosing an alert type and selecting “Set Conditions,” then inspect the network requests while the page is grayed out. The issue mentions 400 responses for “No feature specified” and “Invalid input”; done means the conditions page loads promptly and becomes functional without those errors.

Written by the indexing model from the issue text.