Update documentation of quantum_fisher (#6074)

**Context:**
The documentation of `qinfo.quantum_fisher` was not quite precise on
when `adjoint_metric_tensor` is being used (successfully), and did not
mention potential auxiliary wire requirements.

**Description of the Change:**
Make the criterion on using default.qubit precise (because we catch
other devices), and mention that for other settings, an auxiliary wire
may be required.

**Benefits:**

**Possible Drawbacks:**

**Related GitHub Issues:**
#6059 
[sc-70300]

doc/releases/changelog-dev.md

@@ -266,6 +266,10 @@
 
 <h3>Documentation 📝</h3>
 
+* Improves the docstring for `qinfo.quantum_fisher` regarding the internally used functions and
+  potentially required auxiliary wires.
+  [(#6074)](https://github.com/PennyLaneAI/pennylane/pull/6074)
+
 * Improves the docstring for `QuantumScript.expand` and `qml.tape.tape.expand_tape`.
   [(#5974)](https://github.com/PennyLaneAI/pennylane/pull/5974)
 

pennylane/gradients/fisher.py

@@ -305,9 +305,12 @@ def quantum_fisher(
 
     .. note::
 
-        ``quantum_fisher`` coincides with the ``metric_tensor`` with a prefactor of :math:`4`. Internally, :func:`~.pennylane.adjoint_metric_tensor` is used when executing on a device with
-        exact expectations (``shots=None``) that inherits from ``"default.qubit"``. In all other cases, i.e. if a device with finite shots is used, the hardware compatible transform :func:`~.pennylane.metric_tensor` is used.
-        Please refer to their respective documentations for details on the arguments.
+        ``quantum_fisher`` coincides with the ``metric_tensor`` with a prefactor of :math:`4`.
+        Internally, :func:`~.pennylane.adjoint_metric_tensor` is used when executing on ``"default.qubit"``
+        with exact expectations (``shots=None``). In all other cases, e.g. if a device with finite shots
+        is used, the hardware-compatible transform :func:`~.pennylane.metric_tensor` is used, which
+        may require an additional wire on the device.
+        Please refer to the respective documentations for details.
 
     **Example**
 

pennylane/qinfo/transforms.py

@@ -651,9 +651,12 @@ def quantum_fisher(
 
     .. note::
 
-        ``quantum_fisher`` coincides with the ``metric_tensor`` with a prefactor of :math:`4`. Internally, :func:`~.pennylane.adjoint_metric_tensor` is used when executing on a device with
-        exact expectations (``shots=None``) that inherits from ``"default.qubit"``. In all other cases, i.e. if a device with finite shots is used, the hardware compatible transform :func:`~.pennylane.metric_tensor` is used.
-        Please refer to their respective documentations for details on the arguments.
+        ``quantum_fisher`` coincides with the ``metric_tensor`` with a prefactor of :math:`4`.
+        Internally, :func:`~.pennylane.adjoint_metric_tensor` is used when executing on ``"default.qubit"``
+        with exact expectations (``shots=None``). In all other cases, e.g. if a device with finite shots
+        is used, the hardware-compatible transform :func:`~.pennylane.metric_tensor` is used, which
+        may require an additional wire on the device.
+        Please refer to the respective documentations for details.
 
     **Example**