[3.13] gh-140241: Fix documentation for the registry parameter of warnings.warn_explicit() (GH-140242) (GH-140293)

(cherry picked from commit 78e1d65)

Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>
Co-authored-by: Petr Viktorin <encukou@gmail.com>

Author: 3 people

Doc/library/warnings.rst

@@ -469,14 +469,21 @@ Available Functions
 .. function:: warn_explicit(message, category, filename, lineno, module=None, registry=None, module_globals=None, source=None)
 
    This is a low-level interface to the functionality of :func:`warn`, passing in
-   explicitly the message, category, filename and line number, and optionally the
-   module name and the registry (which should be the ``__warningregistry__``
-   dictionary of the module).  The module name defaults to the filename with
-   ``.py`` stripped; if no registry is passed, the warning is never suppressed.
+   explicitly the message, category, filename and line number, and optionally
+   other arguments.
    *message* must be a string and *category* a subclass of :exc:`Warning` or
    *message* may be a :exc:`Warning` instance, in which case *category* will be
    ignored.
 
+   *module*, if supplied, should be the module name.
+   If no module is passed, the filename with ``.py`` stripped is used.
+
+   *registry*, if supplied, should be the ``__warningregistry__`` dictionary
+   of the module.
+   If no registry is passed, each warning is treated as the first occurrence,
+   that is, filter actions ``"default"``, ``"module"`` and ``"once"`` are
+   handled as ``"always"``.
+
    *module_globals*, if supplied, should be the global namespace in use by the code
    for which the warning is issued.  (This argument is used to support displaying
    source for modules found in zipfiles or other non-filesystem import