Probably not your expert answer here, but it may help you out. As far as I am aware, critical path is an inherent part of primavera and there is not button to click to make that go away (nor is it in your best interest to do so). However, I understand what you give to the client can often be contractual or they are very particular about what they are seeing. (I once had a client insist that they did not want relationships between activities) What you can do is change the bars/colors on your chart to simply show "Remaining Work" instead of "Critical Remaining Work" and therefore it will just categorize all the remaining work the same and not show a difference between what is critical vs. normal.
If you wish to display the bars but don't want the red the right-click on the Gantt chart, select Bars, highlight the Remaining Critical Path bar and change the color to one more acceptable to your purpose.