Remove qtpurchasing submodule from qt5

Qt purchasing was not part of Qt 6, and will be moved as a demo/example
under qtdoc, thus we don't need it here.

Task-number: QTBUG-84776
Pick-to: 6.2
Change-Id: Ie6f704e72914072e7e105763ffaeae1d13cff086
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>
Reviewed-by: Alex Blasche <alexander.blasche@qt.io>
Reviewed-by: Rami Potinkara <rami.potinkara@qt.io>

.gitmodules

@@ -200,13 +200,6 @@
 	url = ../qtquickcontrols2.git
 	branch = dev
 	status = essential
-[submodule "qtpurchasing"]
-	depends = qtbase
-	recommends = qtdeclarative
-	path = qtpurchasing
-	url = ../qtpurchasing.git
-	branch = dev
-	status = ignore
 [submodule "qtcharts"]
 	depends = qtbase
 	recommends = qtdeclarative qtmultimedia