coin: Switch vcpkg registry mirror to qtbuildsystem one

It's a new fork under a qtbuildsystem group, but with the contents of
the aledelev fork.

The older mrmsdbdl fork is not used anymore, so it's removed.

Pick-to: 6.8
Change-Id: I641cf8b86e3809f399cfddbe6c5d71ee6174917c
Reviewed-by: Joerg Bornemann <joerg.bornemann@qt.io>
(cherry picked from commit ef53692f29)

coin/provisioning/common/shared/vcpkg/vcpkg-configuration.json

@@ -2,7 +2,7 @@
   "$schema": "https://raw.githubusercontent.com/microsoft/vcpkg-tool/main/docs/vcpkg-configuration.schema.json",
   "default-registry": {
     "kind": "git",
-    "repository": "https://git.qt.io/aledelev/vcpkg",
+    "repository": "https://git.qt.io/qtbuildsystem/vcpkg",
     "baseline": "9c5c2a0ab75aff5bcd08142525f6ff7f6f7ddeee"
   },
   "overlay-triplets": [ "./../triplets" ]

coin/provisioning/common/shared/vcpkg_registry_mirror.txt

@@ -1,2 +1 @@
-https://git.qt.io/aledelev/vcpkg.git
-https://git.qt.io/mrmsdbdl/vcpkg-mirror.git
+https://git.qt.io/qtbuildsystem/vcpkg.git