As a developer, what do you do when a non-dev asks you to update something in the project?

This is a great question and depends on what kind of tools are being used, how complex the code is, what type of text is being changed and how frequently such changes need to be made. If, for example, we're talking about marketing text (or similar), it's understood that such text would need to be changed frequently and probably A/B tested. In this case, tools should be implemented by the developer which allow non-devs to conduct these experiments in coordination with the marketing team. If we're talking about product-related text, like micro copy for example, then perhaps the dev should provide the non-dev with a simple interface for updating this from time to time. Other than that, if we're talking about sporadic text changes that usually stay static for a long time, the developer might prefer to just update the text quickly. I have found myself in all of these situations at certain points in time and the best approach is usually dictated by these variable circumstances as well as the overall position of the company at the time, with special consideration being given to available development resources.