Bump github.com/stretchr/testify from 1.4.0 to 1.6.1 (#824)

* Bump github.com/stretchr/testify from 1.4.0 to 1.6.1

Bumps [github.com/stretchr/testify](https://github.com/stretchr/testify) from 1.4.0 to 1.6.1.
- [Release notes](https://github.com/stretchr/testify/releases)
- [Commits](https://github.com/stretchr/testify/compare/v1.4.0...v1.6.1)

Signed-off-by: dependabot[bot] <support@github.com>

* Update go.mod

* math.Inf(1)+math.Inf(-1)=NaN

Math is hard

* Remove indirect transitive dependency

* Auto-fix go.sum changes in dependent modules

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Liz Fong-Jones <lizf@honeycomb.io>
Co-authored-by: Evan Torrie <evantorrie@users.noreply.github.com>
Co-authored-by: Joshua MacDonald <jmacd@users.noreply.github.com>

sdk/metric/aggregator/array/array_test.go

@@ -260,7 +260,6 @@ func TestArrayFloat64(t *testing.T) {
 		// points except for NaN, which is invalid.
 		return []float64{
 			0,
-			math.Inf(sign),
 			1 / math.Inf(sign),
 			1,
 			2,