Removed reference to output devices from description of the synthesiz…

…er dialog (nvaccess#17186)

Section 12.1.2.2, "Change synthesizer" of NVDA's User Guide currently reads:

[...] This button activates the Select Synthesizer dialog, which allows you to select the active speech synthesizer and output device. [...]

Even though output device selection has been moved to NVDA's audio settings.

Description of user facing changes
The outdated reference to changing the audio output device via the speech synthesizer dialog has been removed.

Description of development approach
Removed the words "and output device" from the description of the synthesizer section of the speech page of NVDA's settings in user_docs/en/userGuide.md.

user_docs/en/userGuide.md

@@ -1846,7 +1846,8 @@ The Speech Settings category contains the following options:
 
 ##### Change synthesizer {#SpeechSettingsChange}
 
-The first option in the Speech Settings category is the Change... button. This button activates the [Select Synthesizer](#SelectSynthesizer) dialog, which allows you to select the active speech synthesizer and output device.
+The first option in the Speech Settings category is the Change... button.
+This button activates the [Select Synthesizer](#SelectSynthesizer) dialog, which allows you to select the active speech synthesizer.
 This dialog opens on top of the NVDA Settings dialog.
 Saving or dismissing the settings in the Select Synthesizer dialog will return you to the NVDA Settings dialog.