MAINT: remove upper limit of pytest (#115)

* MAINT: remove upper limit of pytest

* MAINT: update actions' versions

* Update .github/workflows/tests.yml

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Co-authored-by: Angus Hollands <goosey15@gmail.com>

Author: bsipocz

pyproject.toml

@@ -71,7 +71,7 @@ testing = [
     "nbformat>=5.1",
     "numpy",
     "pandas",
-    "pytest>=6,<8",
+    "pytest>=6",
     "pytest-cov",
     "pytest-regressions",
     "sympy",