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/shells/oh/deps.json

@@ -1,10 +1,29 @@
 [
-  {
-    "include": "../../libs.json",
-    "packages": [
-      "github.com/michaelmacinnis/adapted",
-      "github.com/peterh/liner",
-      "golang.org/x/sys"
-    ]
-  }
+    {
+        "goPackagePath": "golang.org/x/sys",
+        "fetch": {
+            "type": "git",
+            "url": "https://go.googlesource.com/sys",
+            "rev": "d9157a9621b69ad1d8d77a1933590c416593f24f",
+            "sha256": "1asdbp7rj1j1m1aar1a022wpcwbml6zih6cpbxaw7b2m8v8is931"
+        }
+    },
+    {
+        "goPackagePath": "github.com/michaelmacinnis/adapted",
+        "fetch": {
+            "type": "git",
+            "url": "https://github.com/michaelmacinnis/adapted",
+            "rev": "0dd5fa34d6f9d74c7c0deed1fc224f9a87e02978",
+            "sha256": "16n3a87m33pqx4qih713q3gw2j6ksj1q3ngjax6bpn5b11rqvikv"
+        }
+    },
+    {
+        "goPackagePath": "github.com/peterh/liner",
+        "fetch": {
+            "type": "git",
+            "url": "https://github.com/peterh/liner",
+            "rev": "ad1edfd30321d8f006ccf05f1e0524adeb943060",
+            "sha256": "0c24d9j1gnq7r982h1l2isp3d37379qw155hr8ihx9i2mhpfz317"
+        }
+    }
 ]