Fixed nasty popping between every voice prompt and after every silence.

When retrieving the codec2 data, ensure it is an exact multiple of codec2 frames and always discard the very last frame.

openrtx/src/core/voicePrompts.c

@@ -488,8 +488,8 @@ void vp_tick()
 
             vpCurrentSequence.c2DataIndex  = 0;
             vpCurrentSequence.c2DataStart  = tableOfContents[promptNumber];
-            vpCurrentSequence.c2DataLength = tableOfContents[promptNumber + 1]
-                                           - tableOfContents[promptNumber];
+            vpCurrentSequence.c2DataLength = ((tableOfContents[promptNumber + 1]
+                                           - tableOfContents[promptNumber])/8 * 8);
         }
 
         while (vpCurrentSequence.c2DataIndex < vpCurrentSequence.c2DataLength)