deps: Bump hcl2json to v0.6.5

[jalseth]

This is a breaking change for Rego policies that check HCL2 syntax. The new input always uses arrays instead of conditionally using arrays only when a HCL block has more than one element with the same name.

This will not be merged until the April release as this is a breaking change. The March release will contain a breakage announcement.

Fixes: #1006
Relates to: #1014

[boranx]

Thanks for organizing it into a more generic table-driven form!
Besides, +1 to use parsers' unmarshal and leaning on map[string]any instead of intermediate JSON conversions and indentation steps in tests in general.
Also, +1 to use Google's cmp to subtract diff instead of printing out all the inputs/outputs in verbose mode. We can expand it to all the test suites as part of our test conventions

In the meantime, I was thinking in parallel how can we introduce this type of breaking changes related to parsing behaviours in our docs. Would it make sense if each parser had its own section explaining the basic transformation process and caveats, as well as recent behavioral changes?

LGTM, neat