Reset C-, only for the org-mode case

[michael-franzese]

Have been using the following keybindings to change the text height.

(global-set-key (kbd "C-,") 'text-scale-decrease)
(global-set-key (kbd "C-.") 'text-scale-increase)

But in org-mode C-, is already being used for org-cycle-agenda-files

C-'
C-, (org-cycle-agenda-files)

It was suggested to me that I can reset C-, and then apply my new keybinding
to execute "text-scale-decrease".

I would like to reset C-, only for the org-mode case.  What can be done?