Removing borders from rasters created in Classification Wizard

[ChloéeLabonté]

Hello,

I am unable to remove the white and black borders (see image) from the raster I created using Classification Wizard on ArcGIS Pro. I have already tried the following pathway: Right click the layer > “symbology” > “mask” tab >  Choose “No Colour” for the “Nodata” box. 

Thank you in advance for your help!