Tested on Windows Server 2016.
The source mentions it also should work on Vista, 7, and 8.

Change the TileInfo REG_SZ registry key under HKEY_LOCAL_MACHINE\Software\Classes\Drive.

The default value is:

prop:*System.PercentFull;System.Computer.DecoratedFreeSpace;System.Volume.FileSystem

To remove the percentage indicator, change it to:

prop:*System.Computer.DecoratedFreeSpace;System.Volume.FileSystem

To also remove the mention of the type of filesystem, change it to:

prop:*System.Computer.DecoratedFreeSpace

Source: SumTips - Windows: Disable Drive Space Indicator Bar