Fix missing network references

* Add missing references to LeNet
* Remove mnist example, which is an internally developed network

Resolves: COMPMID-4559

Signed-off-by: SiCongLi <sicong.li@arm.com>
Change-Id: I139354890f1a9acb54a87add6895262102b3b8de
Reviewed-on: https://review.mlplatform.org/c/ml/ComputeLibrary/+/5782
Reviewed-by: Georgios Pinitas <georgios.pinitas@arm.com>
Tested-by: Georgios Pinitas <georgios.pinitas@arm.com>
diff --git a/examples/graph_lenet.cpp b/examples/graph_lenet.cpp
index 6560a98..1bcd95f 100644
--- a/examples/graph_lenet.cpp
+++ b/examples/graph_lenet.cpp
@@ -132,6 +132,14 @@
 
 /** Main program for LeNet
  *
+ * Model is based on:
+ *      http://yann.lecun.com/exdb/publis/pdf/lecun-98.pdf
+ *      "Gradient-Based Learning Applied to Document Recognition"
+ *      Yann LeCun, Léon Bottou, Yoshua Bengio, and Patrick Haffner
+ *
+ * The original model uses tanh instead of relu activations. However the use of relu activations in lenet has been
+ * widely adopted to improve accuracy.*
+ *
  * @note To list all the possible arguments execute the binary appended with the --help option
  *
  * @param[in] argc Number of arguments