chore(dependencies): restrict yanked pytest version 8.1.0 (#143)

* pytest 8.1.0 broke some plugins and was yanked
* https://github.com/pytest-dev/pytest/releases/tag/8.1.0
* always install examples dependencies in ci (need flopy)

.github/workflows/ci.yml

@@ -151,7 +151,6 @@ jobs:
           key: modflow6-examples-${{ hashFiles('modflow6-examples/data/**') }}
 
       - name: Install extra Python packages
-        if: steps.cache-examples.outputs.cache-hit != 'true'
         working-directory: modflow6-examples/etc
         run: |
           pip install -r requirements.pip.txt

pyproject.toml

@@ -58,7 +58,7 @@ test = [
     "meson!=0.63.0",
     "ninja",
     "numpy",
-    "pytest",
+    "pytest!=8.1.0",
     "pytest-cov",
     "pytest-dotenv",
     "pytest-xdist",