gnu: KDE: Fix old cgit home-pages.

gnu: KDE: Fix old cgit home-pages.

Fix all home-pages pointing to git-repos a cgit.kde.org, which is
gone, to now use the correct repo at invent.kde.org.

* gnu/packages/kde.scm (grantleetheme, kdiagram): Update home-page.
* gnu/packages/kde-frameworks.scm (kholidays): Likewise.
* gnu/packages/kde-internet.scm (libgravatar, libktorrent): Likewise.
* gnu/packages/kde-multimedia.scm (libkcddb, libkcompactdisc): Likewise.
* gnu/packages/kde-pim.scm (kblog, kdav, kdepim-apps-libs,
  kdepim-runtime, keventviews, kincidenceeditor, kmailcommon,
  kmailimporter, kmessagelib, kpimcommon, ksmtp, libkdepim, libkgapi,
  libkleo, libksieve): Likewise.
* gnu/packages/kde-plasma.scm (kdecoration, kscreenlocker): Likewise.