limit pytest version to <8.1 (treeverse#10334)

Change in pytest==8.1.0 breaks `flaky` plugin.

See box/flaky#198.

Author: skshetry

pyproject.toml

@@ -103,7 +103,7 @@ tests = [
     "dvc-ssh",
     "filelock",
     "flaky",
-    "pytest>=7,<9",
+    "pytest>=7,<8.1",
     "pytest-cov>=4.1.0",
     "pytest-docker>=1,<4",
     "pytest-mock",