add explanatory text for the disable payg modal

Author: VoigtS

src/components/mainView/subComponents/ForbidAutogrowth.js

@@ -104,6 +104,12 @@ const ForbidAutogrowth = (props) => {
         )}
         <p data-testid="forbidAutogrowthConfirmText">
           Do you want to <strong>{autogrowthForbidden ? "disable" : "enable"}</strong> Pay-As-You-Go?
+          {autogrowthForbidden && (
+            <div className="text-sm mt-2">
+              Disabling will limit your available quota to either your existing commitments or your current usage,
+              whichever value is greater.
+            </div>
+          )}
         </p>
       </Modal>
     </>