style: silence ruff-specific warning

RUF003 Comment contains ambiguous `’` (RIGHT SINGLE QUOTATION MARK).
       Did you mean ``` (GRAVE ACCENT)?

Doesn't make much sense, however let's be consistent and use `'`
apostrophes, as in all other code comments.

tests/test_cli.py

@@ -70,7 +70,7 @@ def setUpModule():
     env_vars_that_could_interfere = (
         'YAMLLINT_CONFIG_FILE',
         'XDG_CONFIG_HOME',
-        # These variables are used to determine where the user’s home
+        # These variables are used to determine where the user's home
         # directory is. See
         # https://docs.python.org/3/library/os.path.html#os.path.expanduser
         'HOME',