Revert "temp: mirror erikarvstedt btcpayserver"

This reverts commit 99295328b4.
Removes nbxplorer/btcpayserver from travis
Adds nbxplorer/btcpayserver to pinned.nix

pkgs/default.nix

@@ -1,5 +1,5 @@
 { pkgs ? import <nixpkgs> {} }:
-let self = {
+{
   lightning-charge = pkgs.callPackage ./lightning-charge { };
   nanopos = pkgs.callPackage ./nanopos { };
   spark-wallet = pkgs.callPackage ./spark-wallet { };
@@ -13,13 +13,8 @@ let self = {
   nixops19_09 = pkgs.callPackage ./nixops { };
   netns-exec = pkgs.callPackage ./netns-exec { };
   lightning-loop = pkgs.callPackage ./lightning-loop { };
-  btcpayserver = pkgs.callPackage ./btcpayserver { inherit (self) linkFarmFromDrvs; };
-  nbxplorer = pkgs.callPackage ./nbxplorer { inherit (self) linkFarmFromDrvs; };
-
-  # Temporary backport for btcpayserver
-  linkFarmFromDrvs = pkgs.linkFarmFromDrvs or self.pinned.nixpkgsUnstable.linkFarmFromDrvs;
 
   pinned = import ./pinned.nix;
 
   lib = import ./lib.nix { inherit (pkgs) lib; };
-}; in self
+}