niv motoko-base: update 6f47a697 -> 8d5713b2

## Changelog for motoko-base:
Branch: next-moc
Commits: [dfinity/motoko-base@6f47a697...8d5713b2](dfinity/motoko-base@6f47a69...8d5713b)

* [`318b4eec`](dfinity/motoko-base@318b4ee) Motoko 0.14.1

nix/sources.json

@@ -75,10 +75,10 @@
         "homepage": "",
         "owner": "dfinity",
         "repo": "motoko-base",
-        "rev": "6f47a697a08b72e1f008402a85547b84d1edbbd8",
-        "sha256": "1y0x5ans7na264baha1zjdhlhbcvsba4j9vgnyz8j57f7cdxrnva",
+        "rev": "8d5713b2eb75104fb32d3cb988bb6b406e1450bd",
+        "sha256": "1qfhjk8z7dlp15b9c9lil2zx96dj7w0xdgpv152h7g8igzq956as",
         "type": "tarball",
-        "url": "https://github.com/dfinity/motoko-base/archive/6f47a697a08b72e1f008402a85547b84d1edbbd8.tar.gz",
+        "url": "https://github.com/dfinity/motoko-base/archive/8d5713b2eb75104fb32d3cb988bb6b406e1450bd.tar.gz",
         "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
     },
     "motoko-matchers": {