Remove duplicate docstring

Author: davidhassell

cf/docstring/docstring.py

@@ -686,19 +686,4 @@
                      The subspace is the smallest hyperrectangular
                      subspace that contains all of the selected
                      locations.""",
-    # read filesystem
-    "{{read filesystem: optional}}": """filesystem: optional
-            A pre-authenticated filesystem object (for example an
-            ``fsspec`` filesystem instance) to use for opening the
-            dataset. When provided, *datasets* values are treated as
-            paths understood by *filesystem*, and local string
-            pre-processing (tilde/variable expansion, globbing and
-            directory walking) is bypassed. The file is opened by
-            calling ``filesystem.open(dataset, "rb")``, which returns
-            a file-like object that is passed to the netCDF backend.
-
-            If `None` (the default) then the existing file-opening
-            logic is used.
-
-            .. versionadded:: NEXTVERSION""",
 }