tdesktopPackages.preview: 1.4.4 -> 1.4.7

TODO: We're still using the old API ID (like the Arch package) which
should be used for testing only.
I've tried to contact the Telegram team multiple times via different
channels but didn't get a response so far. See [0],[1] for more details.

[0]: https://github.com/telegramdesktop/tdesktop/issues/4717
[1]: 65b2db2160

pkgs/applications/networking/instant-messengers/telegram/tdesktop/default.nix

@@ -13,8 +13,8 @@ let
 in {
   stable = mkTelegram stableVersion;
   preview = mkTelegram (stableVersion // {
-    version = "1.4.4";
-    sha256Hash = "1m1j485r3vzpglzfn8l4cqskysvkx8l3pqaw3fgp66jfajbxynf0";
+    version = "1.4.7";
+    sha256Hash = "00kjirikywdbigm4zdnm50s3wxfn9bw1yx13xz4k4ppz6amq9nrp";
     stable = false;
   });
 }

pkgs/applications/networking/instant-messengers/telegram/tdesktop/generic.nix

@@ -97,7 +97,9 @@ mkDerivation rec {
     sed -i Telegram/ThirdParty/libtgvoip/libtgvoip.gyp \
       -e "/-msse2/d"
 
-    gyp \
+    gyp ${lib.optionalString (!stable) ''
+        -Dapi_id=17349 \
+        -Dapi_hash=344583e45741c457fe1862106095a5eb ''}\
       -Dbuild_defines=${GYP_DEFINES} \
       -Gconfig=Release \
       --depth=Telegram/gyp \