docs: Add v0.7.2 failing example to v0.7.3 release notes (#2294)

* As the bug that was fixed in PR #2278 was subtle add an example to
the pyhf v0.7.3 release notes that people can use to see if they
were affected by it.
* Amends PR #2290

Author: matthewfeickert

docs/release-notes/v0.7.3.rst

@@ -14,6 +14,55 @@ Fixes
   are correctly handled.
   (PRs :pr:`2277`, :pr:`2278`)
 
+  The fixed bug was subtle and only occurred for specific configurations of
+  settings and arguments where ``do_grad=False`` was used (either explicitly
+  by provided kwarg or implicitly through defaults).
+  To determine if you might have been affected by it, check your code for
+  setups like the following.
+
+  .. code:: python
+
+    # Bug is backend independent. JAX is selected as an example where
+    # do_grad=False might be selected in response to the backend's value of
+    # pyhf.tensorlib.default_do_grad being True.
+    pyhf.set_backend("jax", pyhf.optimize.minuit_optimizer(strategy=0))
+
+    ...
+
+    fit_result, opt_result = pyhf.infer.mle.fit(
+        data, model, return_result_obj=True, do_grad=False
+    )
+    assert opt_result.minuit.strategy.strategy == 0  # fails for pyhf v0.7.2
+
+  Full example that fails in ``pyhf`` ``v0.7.2``:
+
+  .. code:: python
+
+    import pyhf
+
+    pyhf.set_backend("jax", pyhf.optimize.minuit_optimizer(strategy=0))
+
+    model = pyhf.simplemodels.uncorrelated_background(
+        signal=[12.0, 11.0], bkg=[50.0, 52.0], bkg_uncertainty=[3.0, 7.0]
+    )
+    data = [51, 48] + model.config.auxdata
+
+    # passing with strategy kwarg explicitly given
+    fit_result, opt_result = pyhf.infer.mle.fit(
+        data, model, return_result_obj=True, do_grad=False, strategy=0
+    )
+    minuit_strategy = opt_result.minuit.strategy.strategy
+    print(f"# Minuit minimization strategy: {minuit_strategy}")
+    assert minuit_strategy == 0
+
+    # strategy kwarg not given
+    fit_result, opt_result = pyhf.infer.mle.fit(
+        data, model, return_result_obj=True, do_grad=False
+    )
+    minuit_strategy = opt_result.minuit.strategy.strategy
+    print(f"# Minuit minimization strategy: {minuit_strategy}")
+    assert minuit_strategy == 0  # fails for pyhf v0.7.2
+
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