guiconstants: update ORG_DOMAIN to bitcoincore.org

[MarnixCroes]

if desired, can also update ORG_NAME to Bitcoin Core

[DrahtBot]

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[laanwj]

if desired, can also update ORG_NAME to Bitcoin Core

The reason that this was never done is because it changes where the Qt settings files are stored. For example this is ~/.config/<ORG_NAME>/<APP_NAME> on Linux.

i'm not sure what actually is the effect of changing the domain, but this shouldn't be done without checking what it is used for.

[hebasto]

if desired, can also update ORG_NAME to Bitcoin Core

Are there any issues with the current code? If not, then this PR lacks motivation.

[MarnixCroes]

ok, it came across in the qt-qml repo, I looked here and assumed it was forgotten to be updated.
nvm

[laanwj]

Right. i think qt-qml does something substantially different with regard to settings, so it may be warranted there.