Bump go.opentelemetry.io/build-tools/multimod in /internal/tools (#158)

Bumps [go.opentelemetry.io/build-tools/multimod](https://github.com/open-telemetry/opentelemetry-go-build-tools) from 0.12.0 to 0.13.0.
- [Release notes](https://github.com/open-telemetry/opentelemetry-go-build-tools/releases)
- [Changelog](https://github.com/open-telemetry/opentelemetry-go-build-tools/blob/main/CHANGELOG.md)
- [Commits](open-telemetry/opentelemetry-go-build-tools@v0.12.0...v0.13.0)

---
updated-dependencies:
- dependency-name: go.opentelemetry.io/build-tools/multimod
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

internal/tools/go.mod

@@ -4,5 +4,5 @@ go 1.16
 
 require (
 	go.opentelemetry.io/build-tools/dbotconf v0.12.0
-	go.opentelemetry.io/build-tools/multimod v0.12.0
+	go.opentelemetry.io/build-tools/multimod v0.13.0
 )