How to remove the red text when
recording to AVI video?

As a full version, you could get rid of the red text when recording to AVI video. Please do exactly as the following steps,

Step 1 - please click the "Options" icon on the toolbar or click the "Options > Record ..." menu item. See the following screenshot,

Step 2 - after the step 1, the options dialog will be opened. Then uncheck the item "Add Text On Video". See the screenshot below.

Step 3 - after the step 2, click the "OK" button to save the settings and return. See the screenshot below.

Step 4 - after the step 3, you can start recording without red text added now!