Issue #26679: Fix description of KEY_PPAGE and KEY_NPAGE constants

Patch by Robert Bachmann and SilentGhost.
diff --git a/Doc/library/curses.rst b/Doc/library/curses.rst
index e8dfd83..144f7f8 100644
--- a/Doc/library/curses.rst
+++ b/Doc/library/curses.rst
@@ -1508,9 +1508,9 @@
 +------------------+-----------+
 | :kbd:`End`       | KEY_END   |
 +------------------+-----------+
-| :kbd:`Page Up`   | KEY_NPAGE |
+| :kbd:`Page Up`   | KEY_PPAGE |
 +------------------+-----------+
-| :kbd:`Page Down` | KEY_PPAGE |
+| :kbd:`Page Down` | KEY_NPAGE |
 +------------------+-----------+
 
 The following table lists characters from the alternate character set. These are