Bump otel/opentelemetry-collector-contrib in /tests

Bumps otel/opentelemetry-collector-contrib from 0.103.1 to 0.104.0.

---
updated-dependencies:
- dependency-name: otel/opentelemetry-collector-contrib
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>

tests/Dockerfile

@@ -1,3 +1,3 @@
 # syntax=docker/dockerfile:1.6
 # this is here so we can grab the latest version of the collector and have dependabot keep it up to date
-FROM otel/opentelemetry-collector-contrib:0.103.1
+FROM otel/opentelemetry-collector-contrib:0.104.0