fix doctests by making them more realistic

Author: d-v-b

docs/user-guide/arrays.rst

@@ -238,6 +238,8 @@ built-in delta filter::
 
    >>> import lzma
    >>> from numcodecs.zarr3 import LZMA
+   >>> import warnings
+   >>> warnings.filterwarnings("ignore", category=UserWarning)
    >>>
    >>> lzma_filters = [dict(id=lzma.FILTER_DELTA, dist=4), dict(id=lzma.FILTER_LZMA2, preset=1)]
    >>> compressors = LZMA(filters=lzma_filters)

docs/user-guide/consolidated_metadata.rst

@@ -27,6 +27,8 @@ In Python, the consolidated metadata is available on the ``.consolidated_metadat
 attribute of the ``GroupMetadata`` object.
 
    >>> import zarr
+   >>> import warnings
+   >>> warnings.filterwarnings("ignore", category=UserWarning)
    >>>
    >>> store = zarr.storage.MemoryStore()
    >>> group = zarr.create_group(store=store)