Fixed a compiler warning

modules/juce_audio_processors/utilities/juce_AudioProcessorValueTreeState.cpp

@@ -68,7 +68,7 @@ struct AudioProcessorValueTreeState::Parameter   : public AudioProcessorParamete
                                                                    : text.getFloatValue());
     }
 
-    String getText (float normalisedValue, int length) const override
+    String getText (float normalisedValue, int /*length*/) const override
     {
         auto v = range.convertFrom0to1 (normalisedValue);
         return valueToTextFunction != nullptr ? valueToTextFunction (v)