doc: getting_started: Switch to upstream DTC tree

With the required patch already being upstream, we can now redirect
users to the standard vanilla DTC tree.

Signed-off-by: Carles Cufi <carles.cufi@nordicsemi.no>
diff --git a/doc/getting_started/installation_win.rst b/doc/getting_started/installation_win.rst
index f844017..036af34 100644
--- a/doc/getting_started/installation_win.rst
+++ b/doc/getting_started/installation_win.rst
@@ -78,15 +78,10 @@
    * Clone and build the DTC::
 
         $ cd ~
-        $ git clone https://github.com/carlescufi/dtc.git
+        $ git clone https://git.kernel.org/pub/scm/utils/dtc/dtc.git
         $ cd dtc
         $ make
 
-   .. note::
-        The repository containing the DTC itself is currently not the standard
-        upstream one due to a required patch. This will be updated once the
-        patch has been accepted.
-
    * Export the location of the DTC::
 
         $ export DTC=~/dtc/dtc