docs and examples use deprecated forms of keyBy

The DataStream example at https://ci.apache.org/projects/flink/flink-docs-stable/dev/datastream_api.html#example-program uses

keyBy(0)

which has been deprecated. There are many other cases of this throughout the docs:

dev/connectors/cassandra.md
dev/parallel.md
dev/stream/operators/index.md
dev/stream/operators/process_function.md
dev/stream/state/queryable_state.md
dev/stream/state/state.md
dev/types_serialization.md
learn-flink/etl.md
ops/scala_shell.md

and also in a number of examples:

AsyncIOExample.java
SideOutputExample.java
TwitterExample.java
GroupedProcessingTimeWindowExample.java
SessionWindowing.java
TopSpeedWindowing.java
WindowWordCount.java
WordCount.java
TwitterExample.scala
GroupedProcessingTimeWindowExample.scala
SessionWindowing.scala
WindowWordCount.scala
WordCount.scala

There are also some uses of keyBy("string"), which has also been deprecated:

dev/connectors/cassandra.md
dev/stream/operators/index.md
dev/types_serialization.md
learn-flink/etl.md

SocketWindowWordCount.java
SocketWindowWordCount.scala
TopSpeedWindowing.scala