How can I delete key from dictionary in .plist file?

Question

I want delete key from IDESourceControlKnownSSHHostsDefaultsKey dictionary from ~/Library/Preferences/com.apple.dt.Xcode.plist file

I wrote there key in this way defaults write com.apple.dt.Xcode IDESourceControlKnownSSHHostsDefaultsKey -dict-add host 'fingerprint'

How can i delete this key? Not whole IDESourceControlKnownSSHHostsDefaultsKey, but only host key from IDESourceControlKnownSSHHostsDefaultsKey dictionary