Bump github.com/stretchr/testify in /exporter/signalfxexporter

Bumps [github.com/stretchr/testify](https://github.com/stretchr/testify) from 1.6.1 to 1.7.1.
- [Release notes](https://github.com/stretchr/testify/releases)
- [Commits](stretchr/testify@v1.6.1...v1.7.1)

---
updated-dependencies:
- dependency-name: github.com/stretchr/testify
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

exporter/signalfxexporter/go.mod

@@ -10,7 +10,7 @@ require (
 	github.com/open-telemetry/opentelemetry-collector-contrib/receiver/k8sclusterreceiver v0.0.0-00010101000000-000000000000
 	github.com/shirou/gopsutil v2.20.9+incompatible
 	github.com/signalfx/com_signalfx_metrics_protobuf v0.0.2
-	github.com/stretchr/testify v1.6.1
+	github.com/stretchr/testify v1.7.1
 	go.opentelemetry.io/collector v0.12.1-0.20201012183541-526f34200197
 	go.uber.org/multierr v1.6.0
 	go.uber.org/zap v1.16.0

exporter/signalfxexporter/go.sum

@@ -1059,8 +1059,9 @@ github.com/stretchr/testify v1.3.0/go.mod h1:M5WIy9Dh21IEIfnGCwXGc5bZfKNJtfHm1UV
 github.com/stretchr/testify v1.4.0/go.mod h1:j7eGeouHqKxXV5pUuKE4zz7dFj8WfuZ+81PSLYec5m4=
 github.com/stretchr/testify v1.5.1/go.mod h1:5W2xD1RspED5o8YsWQXVCued0rvSQ+mT+I5cxcmMvtA=
 github.com/stretchr/testify v1.6.0/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
-github.com/stretchr/testify v1.6.1 h1:hDPOHmpOpP40lSULcqw7IrRb/u7w6RpDC9399XyoNd0=
 github.com/stretchr/testify v1.6.1/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
+github.com/stretchr/testify v1.7.1 h1:5TQK59W5E3v0r2duFAb7P95B6hEeOyEnHRa8MjYSMTY=
+github.com/stretchr/testify v1.7.1/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
 github.com/subosito/gotenv v1.2.0 h1:Slr1R9HxAlEKefgq5jn9U+DnETlIUa6HfgEzj0g5d7s=
 github.com/subosito/gotenv v1.2.0/go.mod h1:N0PQaV/YGNqwC0u51sEeR/aUtSLEXKX9iv69rRypqCw=
 github.com/tcnksm/ghr v0.13.0 h1:a5ZbaUAfiaiw6rEDJVUEDYA9YreZOkh3XAfXHWn8zu8=