Update pacman sdf-say package name to speech-dispatcher

On a recent ARCH Linux installation the package name for `spd-say` has changed to [speech-dispatcher](https://archlinux.org/packages/community/x86_64/speech-dispatcher/)

tutorials/audio/text_to_speech.rst

@@ -69,7 +69,7 @@ Distro-specific one-liners
 +------------------+-----------------------------------------------------------------------------------------------------------+
 | **Arch Linux**   | ::                                                                                                        |
 |                  |                                                                                                           |
-|                  |     pacman -S spd-say festival espeakup                                                                   |
+|                  |     pacman -S speech-dispatcher festival espeakup                                                         |
 +------------------+-----------------------------------------------------------------------------------------------------------+