[TF2] Fix wrong sorting behavior of the mute UI

[rockbruno]

The voice mute UI has two issues with the column sorting behavior:

• Time sorting is sorting by the formatted string instead of the underlying seconds value, causing e.g. hour-long sessions to be displayed out of order
• The status sorting doesn't work at all. Although the logic is updating the UI text, it never updates the actual underlying data source, so attempting to sort it always retains whatever order you already have.

This PR fixes both issues.

Before:

After examples:

Fixes ValveSoftware/Source-1-Games#8238