Bump github.com/google/cadvisor in /internal/signalfx-agent

Bumps [github.com/google/cadvisor](https://github.com/google/cadvisor) from 0.47.3 to 0.48.1.
- [Release notes](https://github.com/google/cadvisor/releases)
- [Changelog](https://github.com/google/cadvisor/blob/master/CHANGELOG.md)
- [Commits](google/cadvisor@v0.47.3...v0.48.1)

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

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

internal/signalfx-agent/go.mod

@@ -43,7 +43,7 @@ require (
 	github.com/go-test/deep v1.1.0
 	github.com/gobwas/glob v0.2.4-0.20181002190808-e7a84e9525fe
 	github.com/gogo/protobuf v1.3.2
-	github.com/google/cadvisor v0.47.3
+	github.com/google/cadvisor v0.48.1
 	github.com/gorilla/mux v1.8.0
 	github.com/hashicorp/consul/api v1.25.1
 	github.com/hashicorp/vault v1.14.3 // required for newer google.golang.org/api compatibility