Cannot update existing apperance preset

Description

Current behavior: User appearance presets in pcbnew can not be updated while retaining the same filename. A new, unique filename must be made for each preset update in order to successfully save.

Expected behavior: User presets should be updatable without having to create a new filename for each edit-save.

Steps to reproduce

In PCBNEW:

1. Make a user preset and save it with filename "x". Refer to this as x version 1.
2. Make a change to the appearance display (e.g. toggle a layer view enable)
3. Save the modified appearance configuration with the previous filename "x". Refer to this as x version 2.
4. Make another change to the appearance display, or load a different preset "y".
5. Load preset "x"

--> Version 1 of preset x is loaded. Version 2 was expected to load.

KiCad Version

Application: KiCad PCB Editor (64-bit)

Version: (6.0.0), release build

Libraries:
	wxWidgets 3.1.5

Platform: Windows 10 (build 19041), 64-bit edition, 64 bit, Little endian, wxMSW

	wxWidgets: 3.1.5 (wchar_t,wx containers)
	Boost: 1.76.0
	OCC: 7.5.0
	Curl: 7.78.0-DEV
	ngspice: 35
	Compiler: Visual C++ 1929 without C++ ABI

Build settings:
	KICAD_USE_OCC=ON
	KICAD_SPICE=ON