Use monochrome icons in context menu

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## Feature request

**Which Nextcloud Version are you currently using:** 33.0.0

**Is your feature request related to a problem? Please describe.**
Nextcloud uses colored icons in the context menu (at least on macOS). This sticks out and is inconsistent with all other icons, which are monochrome:

**Describe the solution you'd like**
I would like the Nextcloud icons to be monochrome (at least as on option). In the Settings, there is already an option "Use Monochrome Icons", but apparently this does not include context menu icons (but I think it should).

**Describe alternatives you've considered**
N/A

**Additional context**
Here's the existing setting: