Does that Microphone symbol show up when you play back the video? If not then I would not worry about.
But I found this previous 2016 thread on Reddit that mentions how to remove it. Not sure it is applicable to the new Adrenalin version or not:
Another thread at Linustech also mentioned the same thing about using ALT+Z and settings but I believe it may disable the microphone from working. Not sure, you will need to check it out.
If it does disable the Mic and you need it, then some other User might be able offer a different suggestion. But, in my opinion. as long as the Microphone symbol doesn't show up in the final recording then I don't really see a problem.
You can always open an Online AMD Service Request and see if it is possible to disable the Microphone symbol while recording in AMD Relive from showing from here: https://www.amd.com/en/support/contact-email-form
Open Radeon Software, go to Streaming, Scene Editor, and in the list of elements (on the left side) there will be one that says "Indicator", click the little eye beside it.