On Photoshop for macOS, you can use two shortcuts to cycle through the list of open document windows/tabs.
One is the old Photoshop shortcut that goes back many years, which Trevor mentioned:
Control-Tab
This is listed on the official Photoshop keyboard shortcuts web page:
https://helpx.adobe.com/photoshop/using/default-keyboard-shortcuts.html
Photoshop also supports the standard macOS window cycling shortcut that works in almost any Mac app:
Command-`(accent grave, the top left key of the main key group on most US English keyboards)
This is listed and customizable in macOS System Settings, Keyboard, Keyboard Shortcuts, Keyboard (Move Focus to Next Window shortcut). However, I just tried editing it and although that change is respected by most Mac apps, Photoshop for some reason sticks to Command-`and doesn’t respect the shortcut change in macOS.