assert: remove deprecated build constraints

[alexandear]

Summary

This PR removes outdated build constraints.

Changes

Remove unnecessary // +build comments from files in the assert/yaml package.

Motivation

To cleanup the code.

The "Build constraints" says:

Go versions 1.16 and earlier used a different syntax for build constraints, with a "// +build" prefix. The gofmt command will add an equivalent //go:build constraint when encountering the older syntax.

It's a safe change because the minimum supported version by testify is Go 1.17.

[brackendawson]

I'm not confident enough that there aren't people out there using go <= 1.17. While we express support for 1.19 we wont do things that would break earlier versions when we don't need to.

[alexandear]

I'm not confident enough that there aren't people out there using go <= 1.17. While we express support for 1.19 we wont do things that would break earlier versions when we don't need to.

@brackendawson There are no people who use testify with Go 1.16 and below because it's not possible. It simply does not compile:

❯ go1.16 build ./...
# github.com/stretchr/testify/assert
assert/assertion_compare.go:316:17: obj1Value.CanConvert undefined (type reflect.Value has no field or method CanConvert)
assert/assertion_compare.go:342:17: obj1Value.CanConvert undefined (type reflect.Value has no field or method CanConvert)
assert/assertions.go:100:23: field.IsExported undefined (type reflect.StructField has no field or method IsExported)
note: module requires Go 1.17

[brackendawson]

Ooh, maybe then.

[brackendawson]

@dolmen added both forms of build tag far more recently than we set the go directive to 1.17. Was there a reason for adding the older form that we're not aware of?