UI: Set minimum version for nlohmann_json to 3.11

[RytoEX]

Description

We know this is the minimum version that we require, so we can just fail during configure if somehow an older version is found.

Motivation and Context

See:

• Trivial: Add version requirement for nlohmann/json obs-browser#452

Although we no longer support Ubuntu 22.04 for building or running OBS Studio, we can make the dependency requirement here more obvious at configure time.

Either "UI: " or "cmake: " seemed like acceptable commit prefixes, but I went with UI for now.

How Has This Been Tested?

Tested locally on Windows.

Types of changes

• Tweak (non-breaking change to improve existing functionality)

• Code cleanup (non-breaking change which makes code smaller or more readable)

Checklist:

• My code has been run through clang-format.
• I have read the contributing document.
• My code is not on the master branch.
• The code has been tested.
• All commit messages are properly formatted and commits squashed where appropriate.
• I have included updates to all appropriate documentation.