Update readme to point to dask/dask

Author: phofl

README.md

@@ -1,64 +1,7 @@
 Dask Expressions
 ================
 
-Dask DataFrames with query optimization.
+The Implementation is now the default and only backend for Dask DataFrames and was
+moved to https://github.com/dask/dask.
 
-This is a rewrite of Dask DataFrame that includes query
-optimization and generally improved organization.
-
-More in our blog posts:
-- [Dask Expressions overview](https://blog.dask.org/2023/08/25/dask-expr-introduction)
-- [TPC-H benchmark results vs. Dask DataFrame](https://docs.coiled.io/blog/tpch.html)
-
-Example
--------
-
-```python
-import dask_expr as dx
-
-df = dx.datasets.timeseries()
-df.head()
-
-df.groupby("name").x.mean().compute()
-```
-
-Query Representation
---------------------
-
-Dask-expr encodes user code in an expression tree:
-
-```python
->>> df.x.mean().pprint()
-
-Mean:
-  Projection: columns='x'
-    Timeseries: seed=1896674884
-```
-
-This expression tree will be optimized and modified before execution:
-
-```python
->>> df.x.mean().optimize().pprint()
-
-Div:
-  Sum:
-    Fused(375f9):
-    | Projection: columns='x'
-    |   Timeseries: dtypes={'x': <class 'float'>} seed=1896674884
-  Count:
-    Fused(375f9):
-    | Projection: columns='x'
-    |   Timeseries: dtypes={'x': <class 'float'>} seed=1896674884
-```
-
-Stability
----------
-
-This is the default backend for dask.DataFrame since version 2024.3.0.
-
-API Coverage
-------------
-
-Dask-Expr covers almost everything of the Dask DataFrame API. The only missing features are:
-
-- named GroupBy Aggregations
+This repository is no longer maintained.