Use HTTPS for schema location in global settings.xml

Currently, the default settings.xml uses http for the schemaLocation:

xsi:schemaLocation="http://maven.apache.org/SETTINGS/1.0.0 http://maven.apache.org/xsd/settings-1.0.0.xsd"

This should be changed to https (http://maven.apache.org/xsd/settings-1.0.0.xsd) which is also the URL used in the docs (https://maven.apache.org/settings.html).