Since 64d5926e (Drop support for Go < 1.18) and 3bf6c92d (Add PyDict
mode) ogórek started to require go ≥ 1.18 that added generics. That
release also added `any` type alias for interface{} to increase
signal/noise ratio in the programs where interface{} is frequently used.

Any is aliased to interface{} similarly to how rune is aliased to
int32, and so any and interface{} are fully interchangeable, just any
reads more shorter and concise:

    https://pkg.go.dev/builtin#any

-> Replace interface{} with any throughout the whole codebase for the
   sources to be read more well.

The replacement was done via running the following sed script:

    $ sed -i -e 's/interface{}/any/g' *.go