[FLINK-8849][docs] Fix links to chaining docs

This closes #5630.

docs/concepts/runtime.md

@@ -31,7 +31,7 @@ under the License.
 For distributed execution, Flink *chains* operator subtasks together into *tasks*. Each task is executed by one thread.
 Chaining operators together into tasks is a useful optimization: it reduces the overhead of thread-to-thread
 handover and buffering, and increases overall throughput while decreasing latency.
-The chaining behavior can be configured; see the [chaining docs](../dev/datastream_api.html#task-chaining-and-resource-groups) for details.
+The chaining behavior can be configured; see the [chaining docs](../dev/stream/operators/#task-chaining-and-resource-groups) for details.
 
 The sample dataflow in the figure below is executed with five subtasks, and hence with five parallel threads.
 
@@ -98,7 +98,7 @@ job. Allowing this *slot sharing* has two main benefits:
 
 <img src="../fig/slot_sharing.svg" alt="TaskManagers with shared Task Slots" class="offset" width="80%" />
 
-The APIs also include a *[resource group](../dev/datastream_api.html#task-chaining-and-resource-groups)* mechanism which can be used to prevent undesirable slot sharing. 
+The APIs also include a *[resource group](../dev/stream/operators/#task-chaining-and-resource-groups)* mechanism which can be used to prevent undesirable slot sharing. 
 
 As a rule-of-thumb, a good default number of task slots would be the number of CPU cores.
 With hyper-threading, each slot then takes 2 or more hardware thread contexts.