Update github.com/stretchr/testify to enable suite usage

[thatgim]

Hi!

I just noticed I can't use github.com/stretchr/testify/suite with httpexpect because in v1.5.0 Suite.T() returns a custom wrapper type TestingT.
https://pkg.go.dev/github.com/stretchr/[email protected]/suite#Suite.T
In the latest version this is fixed/better because it just returns a regular *testing.T.
https://pkg.go.dev/github.com/stretchr/[email protected]/suite#Suite.T

[gavv]

Thanks for report, bumped testify to 1.6.0, where this change was first introduced: c251d4b

Closing, feel free to reopen if needed.