Issue #26304: Change "allows to <verb>" to "allows <verb>ing" or similar

The original form is incorrect grammar and feels awkward, even though the
meaning is clear.
diff --git a/Doc/library/signal.rst b/Doc/library/signal.rst
index 8f814df..e3efc8b 100644
--- a/Doc/library/signal.rst
+++ b/Doc/library/signal.rst
@@ -11,7 +11,7 @@
 General rules
 -------------
 
-The :func:`signal.signal` function allows to define custom handlers to be
+The :func:`signal.signal` function allows defining custom handlers to be
 executed when a signal is received.  A small number of default handlers are
 installed: :const:`SIGPIPE` is ignored (so write errors on pipes and sockets
 can be reported as ordinary Python exceptions) and :const:`SIGINT` is