fetchurl: refresh and add extra KDE mirrors

* fetchurl: fix and add extra KDE mirrors (#51480)

- The gwdg.de mirror has moved the relative path of its KDE tarballs
- Add new mirrors from Berkeley and MIT, which are on the list of officially supported mirrors

https://download.kde.org/extra/download-mirrors.html

* More KDE mirror touchups

- The official one is a redirect to HTTPS anyways, so go directly to HTTPS
- Add China USTC for Asian users
- Swap Finland university from FTP to HTTP

* fetchurl: keep one ftp KDE mirror

pkgs/build-support/fetchurl/mirrors.nix

@@ -70,13 +70,15 @@ rec {
     ftp://ftp.funet.fi/pub/mirrors/ftp.kernel.org/pub/
   ];
 
-  # Mirrors of ftp://ftp.kde.org/pub/kde/.
+  # Mirrors from https://download.kde.org/extra/download-mirrors.html
   kde = [
-    "http://download.kde.org/download.php?url="
-    http://ftp.gwdg.de/pub/x11/kde/
-    ftp://ftp.heanet.ie/mirrors/ftp.kde.org/
+    "https://download.kde.org/download.php?url="
+    https://ftp.gwdg.de/pub/linux/kde/
+    https://mirrors.ocf.berkeley.edu/kde/
+    http://mirrors.mit.edu/kde/
+    https://mirrors.ustc.edu.cn/kde/
+    http://ftp.funet.fi/pub/mirrors/ftp.kde.org/pub/kde/
     ftp://ftp.kde.org/pub/kde/
-    ftp://ftp.funet.fi/pub/mirrors/ftp.kde.org/pub/kde/
   ];
 
   # Gentoo files.