Fixed two typos in dfpwm.lua (#2272)

Author: Zirunis

projects/core/src/main/resources/data/computercraft/lua/rom/modules/main/cc/audio/dfpwm.lua

@@ -8,8 +8,8 @@ Convert between streams of DFPWM audio data and a list of amplitudes.
 DFPWM (Dynamic Filter Pulse Width Modulation) is an audio codec designed by GreaseMonkey. It's a relatively compact
 format compared to raw PCM data, only using 1 bit per sample, but is simple enough to encode and decode in real time.
 
-Typically DFPWM audio is read from [the filesystem][`fs.ReadHandle`] or a [a web request][`http.Response`] as a string,
-and converted a format suitable for [`speaker.playAudio`].
+Typically DFPWM audio is read from [the filesystem][`fs.ReadHandle`] or [a web request][`http.Response`] as a string,
+and converted to a format suitable for [`speaker.playAudio`].
 
 ## Encoding and decoding files
 This module exposes two key functions, [`make_decoder`] and [`make_encoder`], which construct a new decoder or encoder.