Use new ppa domain ppa.launchpadcontent.net

[Tibladar]

Launchpad uses a new domain for serving ppa content: https://ppa.launchpadcontent.net ppa.launchpad.net is still (and will be) active but Ubuntu 22.04 is already using the new domain by default

we recommend moving to the new names where possible

See https://blog.launchpad.net/ppa/new-domain-names-for-ppas

The following packages need to be updated to support the new domain (https://github.com/search?q=org%3Alinuxmint+ppa.launchpad.net&type=code):

• MintSources
• MintUpdate
• MintCommon

The old one shouldn't be replaced since it's still valid but deprecated

Currently when having the new domain in a source-list the following is broken:

• editing in mintsources
• changelogs in mintupdate

[clefebvre]

Fixed in mintupdate 5.8.9

[clefebvre]

Fixed in mintsources 2.1.11

[clefebvre]

Fixed in mintcommon 2.1.9