FortranCInterface: Skip appending an unnecessary newline to Output.cmake

Initially identified in !9194 (comment 1474572), the appending of this newline doesn't seem to be needed. The contents as copied by the configure_file() in the line before it should be sufficient. Forcing the appending of a new line would force the timestamp of the file to be updated, which maybe doesn't matter given the logic that prevents re-running the check when it has already been done on a previous run, but it's unnecessary code so let's remove it.