doc: note about mutation of parametrized values (#7516)

Fix #7514 by augmenting Note with behaviour when parametrized values are mutated
(changes are reflected in subsequent test-case calls).

Author: ankostis

doc/en/parametrize.rst

@@ -79,19 +79,30 @@ them in turn:
     FAILED test_expectation.py::test_eval[6*9-42] - AssertionError: assert 54...
     ======================= 1 failed, 2 passed in 0.12s ========================
 
+.. note::
+
+    Parameter values are passed as-is to tests (no copy whatsoever).
+
+    For example, if you pass a list or a dict as a parameter value, and
+    the test case code mutates it, the mutations will be reflected in subsequent
+    test case calls.
+
 .. note::
 
     pytest by default escapes any non-ascii characters used in unicode strings
     for the parametrization because it has several downsides.
-    If however you would like to use unicode strings in parametrization and see them in the terminal as is (non-escaped), use this option in your ``pytest.ini``:
+    If however you would like to use unicode strings in parametrization
+    and see them in the terminal as is (non-escaped), use this option
+    in your ``pytest.ini``:
 
     .. code-block:: ini
 
         [pytest]
         disable_test_id_escaping_and_forfeit_all_rights_to_community_support = True
 
     Keep in mind however that this might cause unwanted side effects and
-    even bugs depending on the OS used and plugins currently installed, so use it at your own risk.
+    even bugs depending on the OS used and plugins currently installed,
+    so use it at your own risk.
 
 
 As designed in this example, only one pair of input/output values fails