pig-latin: Remove call to Printf in tests and use sub-tests

[andrerfcsantos]

While testing solutions locally for the exercises in the track, I noticed that the exercise pig-latin has a direct call to fmt.Printf:

go/exercises/practice/pig-latin/pig_latin_test.go

Line 13 in d631baf

fmt.Printf("PASS: %s\n", test.description)

This makes it so just running go test produces output, which is not desirable. I understand this call to print was probably an attempt to explicitly print which tests failed and which ones passed, but the go command itself can print the result of individual tests in verbose mode with go test -v - the tests themselves shouldn't print if they passed or failed.

While removing this call to print, we can make this exercise use sub-tests, as discussed in #2098

The tasks here are:

• Remove the call to fmt.Printf on the tests
• Remove PASS: and FAIL: from strings - go test -v can provide this kind of output based just on the test (or sub-test) results
• Make exercise use sub-tests (example in Migrate data-driven tests to subtests #2098)

[Satho-M]

I can work on this one if nobody else is already.