Fix doctest requires

Author: dstansby

docs/tutorial.rst

@@ -809,9 +809,9 @@ Another storage alternative is the :class:`zarr.storage.DBMStore` class, added
 in Zarr version 2.2. This class allows any DBM-style database to be used for
 storing an array or group. Here is an example using a Berkeley DB B-tree
 database for storage (requires `bsddb3
-<https://www.jcea.es/programacion/pybsddb.htm>`_ to be installed)::
+<https://www.jcea.es/programacion/pybsddb.htm>`_ to be installed):
 
-.. doctest-requires:: bsddb3
+.. doctest-requires::
 
     >>> import bsddb3
     >>> store = zarr.DBMStore('data/example.bdb', open=bsddb3.btopen)

zarr/storage.py

@@ -2067,7 +2067,7 @@ class DBMStore(Store):
     A different database library can be used by passing a different function to
     the `open` parameter. For example, if the `bsddb3
     <https://www.jcea.es/programacion/pybsddb.htm>`_ package is installed, a
-    Berkeley DB database can be used::
+    Berkeley DB database can be used:
 
     .. doctest-requires:: bsddb3