misc/cgo: replace ioutil.ReadFile with os.ReadFile
misc/cgo: replace ioutil.ReadFile with os.ReadFile

For #45557

Change-Id: I25be5b437fa1c9b0e0c46802a9b37efc2d47bca0
Reviewed-on: https://go-review.googlesource.com/c/go/+/431097
Reviewed-by: Ian Lance Taylor <87e9c6d529889242b7e184afb632328636553ab4@google.com>
Run-TryBot: Ian Lance Taylor <87e9c6d529889242b7e184afb632328636553ab4@google.com>
Auto-Submit: Ian Lance Taylor <87e9c6d529889242b7e184afb632328636553ab4@google.com>
TryBot-Result: Gopher Robot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Reviewed-by: Cherry Mui <d62e63aa42ce272d7b6a5055d97e942b33a34679@google.com>

golang/go,golang/go,golang/go,golang/go,golang/go,golang/go,golang/go,golang/go