Search endpoint return different results for URLs with 'http' and 'http' protocols

This issue is related to #6472.

The API should return the same results for URLs independent of the type of protocol: `http` or `https`.

### Steps to reproduce
1. `curl 'https://hypothes.is/api/search?uri=http%3A%2F%2Fexample.com%2F'`
2. `curl 'https://hypothes.is/api/search?uri=https%3A%2F%2Fexample.com%2F'`

### Expected behaviour
1) and 2) return same annotations.

### Actual behaviour
1) and 2) return different amount of annotations.

### Additional details
In contrast to #6472, this issue is also present when the URL is not encoded. These two requests also return different
amounts of annotations:

- `curl 'https://hypothes.is/api/search?uri=http://example.com/'`
- `curl 'https://hypothes.is/api/search?uri=https://example.com/'`