missing idl-build features "anchor-spl/idl-build" in course docs with anchor v0.30.1

[youngqqcn]

refer: https://www.anchor-lang.com/release-notes/0.30.0

Note that all crates that you use to generate type definitions for the IDL need to be specified in the list of idl-build, e.g. anchor-spl/idl-build, some-program/idl-build , ...

in course Lab of https://www.soldev.app/course/anchor-cpi

idl-build = ["anchor-lang/idl-build", "anchor-spl/idl-build"]