The `programs.git.patdiff` options moved to `programs.patdiff` in 25.11.
Setting the old `enable` option also turned on Git integration
automatically, with a warning asking users to set it explicitly.
Remove the aliases and that automatic enablement ahead of the 26.11
release. Set `programs.patdiff.enableGitIntegration = true` to keep the
Git integration.
Setting a removed option now fails with an error that explains what
to do instead.
