buildGoPackage: remove Go deps file libs.json

After #16017 there were a lot
of comments saying that `nix` would be better than `JSON`
for Go packages dependency sets.
As said in https://github.com/NixOS/nixpkgs/pull/16017#issuecomment-229624046

    > Because of the content-addressable store, if two programs have the
    > same dependency it will already result in the same derivation in
    > the
    > store. Git also has compression in the pack files so it won't make
    > much difference to duplicate the dependencies on disk. And finally
    > most users will just use the binary builds so it won't make any
    > differences to them.

This PR removes `libs.json` file and puts all package dependencies in
theirs `deps.json`.

pkgs/tools/filesystems/go-mtpfs/deps.json

@@ -1,17 +1,20 @@
 [
-  {
-    "include": "../../../go-modules/libs.json",
-    "packages": [
-      "github.com/hanwen/go-fuse"
-    ]
-  },
-  {
-    "goPackagePath": "github.com/hanwen/usb",
-    "fetch": {
-      "type": "git",
-      "url": "https://github.com/hanwen/usb",
-      "rev": "69aee4530ac705cec7c5344418d982aaf15cf0b1",
-      "sha256": "01k0c2g395j65vm1w37mmrfkg6nm900khjrrizzpmx8f8yf20dky"
+    {
+        "goPackagePath": "github.com/hanwen/go-fuse",
+        "fetch": {
+            "type": "git",
+            "url": "https://github.com/hanwen/go-fuse",
+            "rev": "bd746dd8bcc8c059a9d953a786a6156eb83f398e",
+            "sha256": "1dvvclp418j3d02v9717sfqhl6fw6yyddr9r3j8gsiv8nb62ib56"
+        }
+    },
+    {
+        "goPackagePath": "github.com/hanwen/usb",
+        "fetch": {
+            "type": "git",
+            "url": "https://github.com/hanwen/usb",
+            "rev": "69aee4530ac705cec7c5344418d982aaf15cf0b1",
+            "sha256": "01k0c2g395j65vm1w37mmrfkg6nm900khjrrizzpmx8f8yf20dky"
+        }
     }
-  }
 ]