Here are two sledgehammer approaches:
(defun change-log-mode () t)
which redefines change-log-mode to do nothing, and
(fset 'change-log-mode (symbol-function 'fundamental-mode))
which makes change-log-mode turn on fundamental mode instead.
A third approach might be to use an overriding advice.
And a somewhat less drastic approach is to remove all mention of the offending mode from auto-mode-alist:
(require 'cl)
(setq auto-mode-alist
(remove-if (lambda (pair) (eq (cdr pair) 'change-log-mode))
auto-mode-alist))
This way, you are not disabling the mode altogether, but it should never be automatically applied (unless some other mechanism turns it on).