Clarify what "minimal element" means in PriorityQueue.EnqueueDequeue

### Description

PriorityQueue.EnqueueDequeue() does not return the minimum element in this condition. It returns the last added element.

### Reproduction Steps

` var pq= new PriorityQueue();
pq.Enqueue(5, 0);
var r = pq.EnqueueDequeue(6, 0);`

### Expected behavior

r = 5

### Actual behavior

r = 6

### Regression?

_No response_

### Known Workarounds

_No response_

### Configuration

.NET 6
Windows 11 x64

### Other information

_No response_