How do I get rid of the shading of screen after taking screenshot?

You can potentially solve this by entering the following commands in Terminal followed by the Enter or Return key:

defaults write com.apple.screencapture disable-shadow true
killall SystemUIServer

The above commands should solve the issue.

If you want to change back, you can use the following terminal commands:

defaults write com.apple.screencapture disable-shadow false

If the above doesn’t work, you can use any third party image editing app, open the screenshot with the editor and crop off the drop shadow.