niv motoko-base: update 732b86ef -> 6f1d7ec4 (#4621)

## Changelog for motoko-base:
Branch: next-moc
Commits: [dfinity/motoko-base@732b86ef...6f1d7ec4](dfinity/motoko-base@732b86e...6f1d7ec)

* [`d38d7ded`](dfinity/motoko-base@d38d7de) Motoko 0.11.3

nix/sources.json

@@ -75,10 +75,10 @@
         "homepage": null,
         "owner": "dfinity",
         "repo": "motoko-base",
-        "rev": "732b86ef5bf37ddba65eb48fc750d677ad243c96",
-        "sha256": "0h16a8hay3diqph8s7d6sqgsfizl57lj2lwnc0s1ngg10f5c7xpr",
+        "rev": "6f1d7ec4b4fb81dd544fbe0ee6e3b5e26b294b61",
+        "sha256": "17yfsblv3b1726x4y4hgqmcvid6hhdhcsgrr3yl3zhnm2b5v9brc",
         "type": "tarball",
-        "url": "https://github.com/dfinity/motoko-base/archive/732b86ef5bf37ddba65eb48fc750d677ad243c96.tar.gz",
+        "url": "https://github.com/dfinity/motoko-base/archive/6f1d7ec4b4fb81dd544fbe0ee6e3b5e26b294b61.tar.gz",
         "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
     },
     "motoko-matchers": {