Launching "Cleanup Tracks and Vias" is re-filling the zones

Description

Upon launching the "Cleanup Tracks and Vias" dialog, all the zones are refilled. I think it should be kept as another option in the dialog to perform before using this tool.

KiCad Version

Application: KiCad PCB Editor (64-bit)

Version: (6.0.0-rc2-14-ga17a58203b), release build

Libraries:
	wxWidgets 3.1.5
	libcurl/7.78.0-DEV Schannel zlib/1.2.11

Platform: Windows 10 (build 19044), 64-bit edition, 64 bit, Little endian, wxMSW

Build Info:
	Date: Dec 18 2021 20:59:09
	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