Help: Clarify that ENVIRONMENT test properties take ;-separated lists

Follow up commit 79f64cc773 (Help: ENVIRONMENT_MODIFICATION clarify only
supports singular values, 2022-02-23) to specifically call out the list
format.

Issue: #23315

Help/prop_test/ENVIRONMENT.rst

@@ -3,7 +3,7 @@ ENVIRONMENT
 
 Specify environment variables that should be defined for running a test.
 
-If set to a list of environment variables and values of the form
-``MYVAR=value`` those environment variables will be defined while running
-the test.  The environment changes from this property do not affect other
-tests.
+Set to a :ref:`semicolon-separated list <CMake Language Lists>` list
+of environment variables and values of the form ``MYVAR=value``.
+Those environment variables will be defined while running the test.
+The environment changes from this property do not affect other tests.

Help/prop_test/ENVIRONMENT_MODIFICATION.rst

@@ -7,10 +7,11 @@ Specify environment variables that should be modified for running a test. Note
 that the operations performed by this property are performed after the
 :prop_test:`ENVIRONMENT` property is already applied.
 
-If set to a list of environment variables and values of the form
-``MYVAR=OP:VALUE``, where ``MYVAR`` is the case-sensitive name of an
-environment variable to be modified. Entries are considered in the
-order specified in the property's value. The ``OP`` may be one of:
+Set to a :ref:`semicolon-separated list <CMake Language Lists>` of
+environment variables and values of the form ``MYVAR=OP:VALUE``,
+where ``MYVAR`` is the case-sensitive name of an environment variable
+to be modified.  Entries are considered in the order specified in the
+property's value.  The ``OP`` may be one of:
 
   - ``reset``: Reset to the unmodified value, ignoring all modifications to
     ``MYVAR`` prior to this entry. Note that this will reset the variable to