maint: move SomeCRS type alias to avoid FutureRef

- docs are failing due to `SomeCRS` type alias,
  this should maybe fix it?

Author: Kirill888

odc/geo/crs.py

@@ -26,8 +26,6 @@
 
 from .types import XY, Unset
 
-SomeCRS = Union[str, int, "CRS", _CRS, Dict[str, Any]]
-MaybeCRS = Union[SomeCRS, Unset, None]
 EPSG_UNSET = 0
 
 
@@ -395,6 +393,9 @@ class CRSMismatchError(ValueError):
     """
 
 
+SomeCRS = Union[str, int, CRS, _CRS, Dict[str, Any]]
+MaybeCRS = Union[SomeCRS, Unset, None]
+
 # fmt: off
 @overload
 def norm_crs(crs: SomeCRS) -> CRS: ...