Move Zarr up in io.rst (#6289)

* Move Zarr up in io.rst

The existing version had it right down the page, below Iris / Pickle /
et al.

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

Author: max-sixty

doc/contributing.rst

@@ -274,13 +274,13 @@ Some other important things to know about the docs:
       .. ipython:: python
 
           x = 2
-          x ** 3
+          x**3
 
   will be rendered as::
 
       In [1]: x = 2
 
-      In [2]: x ** 3
+      In [2]: x**3
       Out[2]: 8
 
   Almost all code examples in the docs are run (and the output saved) during the