silence sphinx warnings about broken rst (#4448)

Author: keewis

xarray/backends/api.py

@@ -352,8 +352,8 @@ def open_dataset(
     chunks : int or dict, optional
         If chunks is provided, it is used to load the new dataset into dask
         arrays. ``chunks={}`` loads the dataset with dask using a single
-        chunk for all arrays. When using ``engine="zarr"`, setting
-        `chunks='auto'` will create dask chunks based on the variable's zarr
+        chunk for all arrays. When using ``engine="zarr"``, setting
+        ``chunks='auto'`` will create dask chunks based on the variable's zarr
         chunks.
     lock : False or lock-like, optional
         Resource lock to use when reading data from disk. Only relevant when