fix: Ensure empty priority would be interpreted with correct value

[HsiuCL]

Ensure that Empty Priority is Interpreted with the Correct Value

Problem

According to the Obsidian Tasks Document, the order of priority from highest to lowest is as follows:

1. 🔺 for highest priority
2. ⏫ for high priority
3. 🔼 for medium priority
4. use no signifier to indicate no priority
5. 🔽 for low priority
6. ⏬️ for lowest priority

However, prior to the change, the absence of a priority (4.) was not assigned the correct value during sorting, resulting in it consistently appearing below any other tasks with a priority, even those of a lower rank.

Solution and Change

Update the metadata sorting to explicitly use the correct value (i.e., Priority.None) during the sorting process.