make unstablespecificationwarning an instance of zarrfuturewarning

Author: d-v-b

src/zarr/core/dtype/common.py

@@ -14,6 +14,7 @@
 )
 
 from zarr.core.common import NamedConfig
+from zarr.errors import ZarrFutureWarning
 
 EndiannessStr = Literal["little", "big"]
 ENDIANNESS_STR: Final = "little", "big"
@@ -205,7 +206,7 @@ class HasObjectCodec:
     object_codec_id: ClassVar[str]
 
 
-class UnstableSpecificationWarning(FutureWarning): ...
+class UnstableSpecificationWarning(ZarrFutureWarning): ...
 
 
 def v3_unstable_dtype_warning(dtype: object) -> None: