test: use tomli fallback for Python 3.10

tomllib is only in the stdlib from 3.11 onward. Fall back to the tomli
shim (already a transitive dep) so the regression test can import on
the 3.10 leg of the test matrix.

lib/crewai/tests/test_dependency_constraints.py

@@ -8,9 +8,15 @@ to defend against so future maintainers understand why a bound is required.
 
 from __future__ import annotations
 
-import tomllib
+import sys
 from pathlib import Path
 
+
+if sys.version_info >= (3, 11):
+    import tomllib
+else:
+    import tomli as tomllib
+
 import pytest
 from packaging.requirements import Requirement
 from packaging.specifiers import SpecifierSet