docs: fix instructions for opting out of dark mode (#19358)
docs: fix instructions for opting out of dark mode (#19358)

4d8a055 (#19226) introduced incorrect instructions for 'opting out' of dark mode in Electron 7.0.0 and for enabling it on older versions. The boolean values for the `NSRequiresAquaSystemAppearance` key were inverted.
gerhardberger/electron,bpasero/electron,gerhardberger/electron,seanchas116/electron,seanchas116/electron,gerhardberger/electron,bpasero/electron,bpasero/electron,electron/electron,electron/electron,gerhardberger/electron,electron/electron,seanchas116/electron,bpasero/electron,gerhardberger/electron,seanchas116/electron,seanchas116/electron,bpasero/electron,bpasero/electron,bpasero/electron,gerhardberger/electron,electron/electron,seanchas116/electron,electron/electron,gerhardberger/electron,electron/electron,electron/electron