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

Bumps [github.com/stretchr/testify](https://github.com/stretchr/testify) from 1.8.4 to 1.11.1.
- [Release notes](https://github.com/stretchr/testify/releases)
- [Commits](stretchr/testify@v1.8.4...v1.11.1)

---
updated-dependencies:
- dependency-name: github.com/stretchr/testify
  dependency-version: 1.11.1
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

exporter/signalfxexporter/go.mod

@@ -15,7 +15,7 @@ require (
 	github.com/shirou/gopsutil/v3 v3.23.6
 	github.com/signalfx/com_signalfx_metrics_protobuf v0.0.3
 	github.com/signalfx/signalfx-agent/pkg/apm v0.0.0-20230214151822-6a6813cf5bf1
-	github.com/stretchr/testify v1.8.4
+	github.com/stretchr/testify v1.11.1
 	go.opentelemetry.io/collector/component v0.81.0
 	go.opentelemetry.io/collector/config/confighttp v0.81.0
 	go.opentelemetry.io/collector/config/configopaque v0.81.0