Correct output shape in EstimatorQNN tutorial 01 (backport #982) (#983)

* Correct output shape in `EstimatorQNN` tutorial (#982)

(cherry picked from commit 7b57913)

* Change `self._num_features` in ValueError message (backport #981) (#984) (#988)

* Correct `self._num_features` in ValueError (#981)

(cherry picked from commit 56bbed0)

* Update copyright in `base_kernel.py`

---------

Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>

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Co-authored-by: Edoardo Altamura <[email protected]>
Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>

Author: mergify[bot]

docs/tutorials/01_neural_networks.ipynb

@@ -477,7 +477,9 @@
    "id": "7fba01a3",
    "metadata": {},
    "source": [
-    "For the `EstimatorQNN`, the expected output shape for the forward pass is `(1, num_qubits * num_observables)` where `1` in our case is the number of samples:"
+    "For the `EstimatorQNN`, the forward pass returns an array of shape `(batch_size, num_observables)\n",
+    "`, where `batch_size` is the number of input samples (1 in our case) and `num_observables` is the \n",
+    "length of the observables list."
    ]
   },
   {
@@ -563,7 +565,7 @@
    "id": "3612ff46",
    "metadata": {},
    "source": [
-    "For the `EstimatorQNN`, the expected output shape for the forward pass is `(batch_size, num_qubits * num_observables)`:"
+    "In `EstimatorQNN`, the forward pass returns an array of shape `(batch_size, num_observables)`, where `batch_size` is the number of input samples and `num_observables` is the length of the observables list.:"
    ]
   },
   {