Make fsspec a test only dependency

Author: tomwhite

pyproject.toml

@@ -27,7 +27,6 @@ dependencies = [
     "array-api-compat",
     "cloudpickle",
     "donfig",
-    "fsspec",
     "mypy_extensions", # for rechunker
     "ndindex",
     "networkx != 2.8.3, != 2.8.4, != 2.8.5, != 2.8.6, != 2.8.7, != 2.8.8, != 3.0.*, != 3.1.*, != 3.2.*",
@@ -83,6 +82,7 @@ coiled = [
 test = [
     "cubed[diagnostics]",
     "dill",
+    "fsspec",
     "numpy_groupies",
     "pytest",
     "pytest-cov",