Update usage.md

usage.md

@@ -7,7 +7,7 @@ This demo enhances voice recordings using **DeepFilterNet2**, a powerful AI mode
 
 1. **Upload** your noisy audio (`.wav` and `.mp3`) — up to **1 hour long**.
 2. *(Optional)* Add background noise to test the filter.
-3. Click **Submit** to process and compare the **original** and **denoised** results.
+3. Click **Generate** to process and compare the **original** and **denoised** results.
 
 #### 🔹 What It Does