[docs] update information about reveal type & locals in common_issues (#19059)

Previously it was impossible to have these in at runtime (more or
less), but now you can just import one of them.

---------

Co-authored-by: Shantanu <12621235+hauntsaninja@users.noreply.github.com>

Author: wyattscarpenter

docs/source/common_issues.rst

@@ -513,11 +513,15 @@ to see the types of all local variables at once. Example:
    #     b: builtins.str
 .. note::
 
-   ``reveal_type`` and ``reveal_locals`` are only understood by mypy and
-   don't exist in Python. If you try to run your program, you'll have to
-   remove any ``reveal_type`` and ``reveal_locals`` calls before you can
-   run your code. Both are always available and you don't need to import
-   them.
+    ``reveal_type`` and ``reveal_locals`` are handled specially by mypy during
+    type checking, and don't have to be defined or imported.
+
+    However, if you want to run your code,
+    you'll have to remove any ``reveal_type`` and ``reveal_locals``
+    calls from your program or else Python will give you an error at runtime.
+
+    Alternatively, you can import ``reveal_type`` from ``typing_extensions``
+    or ``typing`` (on Python 3.11 and newer)
 
 .. _silencing-linters: