Revert "Added prog-mode-hook"

This reverts commit dc80f89.

Executing two hooks when enabling php-mode causes issues for some
users, such as the duplicated execution of hooks.  You can read

    #37

for more reports on the problems it creates.

php-mode.el

@@ -541,9 +541,7 @@ This is was done due to the problem reported here:
   (set (make-local-variable 'add-log-current-defun-header-regexp)
        php-beginning-of-defun-regexp)
 
-  (run-hooks 'prog-mode-hook)
   (run-hooks 'php-mode-hook))
-
 
 ;; Make a menu keymap (with a prompt string)
 ;; and make it the menu bar item's definition.