CMake 3.27 warns about compatibility with CMake <3.5

[kostasdizas]

Describe the bug
CMake 3.27 released earlier this year drops compatibility with CMake <3.5. jsoncppConfig.cmake.in requires version 3.0. Using it in a project produces a deprecation warning:

  Compatibility with CMake < 3.5 will be removed from a future version of
  CMake.

  Update the VERSION argument <min> value or use a ...<max> suffix to tell
  CMake that the project does not need compatibility with older versions.

To Reproduce
Steps to reproduce the behavior:

1. Using CMake 3.27,

Expected behavior
The project is configured without any warnings.

Desktop (please complete the following information):

• OS: Linux
• Meson version: N/A
• Ninja version: N/A

[daudrain]

Looks to be addressed by #1499

[daudrain]

@baylesj This issue can be marked as resolved since #1499 has been merged into master.