KCMColors: Do not forward the output of editDialogProcess

When we are done editing a colorscheme and save it, dialogProcess outputs in stdout the names of the colorschemes we save.

ForwardedChannels would send those names to the stdout of the main process (the KCM), so the dialogProcess stdout was always empty.

Instead, just use defaults: Separate channels (stdout/stderr) and then just read it as usual.

This then allows the reloading to work.

BUG: 504007 FIXED-IN: 6.4.4