Update links to tutorials repo for SDK 2.6 release [Cherry Pick for 2.6]

Test Plan: !docs-only

Reviewers: #tensorflow, #framework_ip_review_-_any_oss_or_third-party_code_use_has_been_approved, georgep

Reviewed By: #tensorflow, #framework_ip_review_-_any_oss_or_third-party_code_use_has_been_approved, georgep

Maniphest Tasks: T65151

Differential Revision: https://phabricator.sourcevertex.net/D71248

Author: Erik Newton

tensorflow/compiler/plugin/poplar/docs/custom_codelet.rst

@@ -52,7 +52,7 @@ C++ code compiled for, and executed on, the IPU.
 For more information about writing Poplar graph programs and codelets, refer to
 the `Poplar and PopLibs User Guide
 <https://docs.graphcore.ai/projects/poplar-user-guide/>`_ and the `Poplar
-tutorials <https://github.com/graphcore/tutorials/tree/sdk-release-2.5/tutorials/poplar>`_
+tutorials <https://github.com/graphcore/tutorials/tree/sdk-release-2.6/tutorials/poplar>`_
 on the Graphcore GitHub tutorials respository.
 
 Your program must contain a function to build the graph, which will be called
@@ -460,10 +460,10 @@ sections. There are further examples in the Graphcore GitHub tutorials
 repository:
 
 * `Custom op with gradient
-  <https://github.com/graphcore/tutorials/tree/sdk-release-2.5/feature_examples/tensorflow/custom_gradient>`_
+  <https://github.com/graphcore/tutorials/tree/sdk-release-2.6/feature_examples/tensorflow/custom_gradient>`_
 
 * `Custom op with codelet for custom vertex code
-  <https://github.com/graphcore/tutorials/tree/sdk-release-2.5/feature_examples/tensorflow/custom_op>`_
+  <https://github.com/graphcore/tutorials/tree/sdk-release-2.6/feature_examples/tensorflow/custom_op>`_
 
 
 .. _inplace_operations:

tensorflow/compiler/plugin/poplar/docs/perf_training.rst

@@ -98,7 +98,7 @@ array and will contain `x1 - x2` for each iteration in the loop.
 
 See entries in the :ref:`api-section` for more details.
 
-For a more practical example, the Graphcore tutorials repository contains a `detailed tutorial about using infeeds and outfeeds with TensorFlow <https://github.com/graphcore/tutorials/tree/sdk-release-2.5/tutorials/tensorflow2/infeed_outfeed>`_.
+For a more practical example, the Graphcore tutorials repository contains a `detailed tutorial about using infeeds and outfeeds with TensorFlow <https://github.com/graphcore/tutorials/tree/sdk-release-2.6/tutorials/tensorflow2/infeed_outfeed>`_.
 
 
 .. _infeed-simplification: