build: Update lower bound on iminuit to v2.7.0 (#1895)

* Update lower bound on iminuit to v2.7.0 as it is the 'oldest' SemVer release
that has the behavior:
> Minuit.hesse no longer sets the status of the FunctionMinimum unconditionally
> to valid if it was invalid before.

Without this fix, the situation can arise where `Minuit.hesse()` can cause
`Minuit.valid` to be True when it should be False.
* Update tests/constraints.txt to use iminuit==2.7.0.
* Amends PR #1845

Author: matthewfeickert

setup.py

@@ -9,7 +9,7 @@
     'torch': ['torch>=1.10.0'],  # c.f. PR #1657
     'jax': ['jax>=0.2.10', 'jaxlib>=0.1.60,!=0.1.68'],  # c.f. Issue 1501
     'xmlio': ['uproot>=4.1.1'],  # c.f. PR #1567
-    'minuit': ['iminuit>=2.4.0'],  # c.f. PR #1306
+    'minuit': ['iminuit>=2.7.0'],  # c.f. PR #1895
 }
 extras_require['backends'] = sorted(
     set(

tests/constraints.txt

@@ -9,7 +9,7 @@ importlib_resources==1.3.0
 # xmlio
 uproot==4.1.1
 # minuit
-iminuit==2.4.0
+iminuit==2.7.0  # c.f. PR #1895
 # tensorflow
 tensorflow==2.6.5  # c.f. PR #1874
 tensorflow-probability==0.11.0  # c.f. PR #1657