ci: run e2e tests on otel-plugin changes (#631)

The e2e-tests workflow's paths filter omitted otel-plugin/, so any PR
touching only that module (including real code changes, not just dependency
bumps) silently skipped e2e coverage. Add 'otel-plugin/**' to the paths
filter on both the pull_request and push triggers.

Author: hln33

.github/workflows/e2e-tests.yml

@@ -10,6 +10,7 @@ on:
       - 'sdk/**'
       - 'sdk-testing/**'
       - 'sdk-integration-tests/**'
+      - 'otel-plugin/**'
       - 'examples/**'
       - 'pom.xml'
   push:
@@ -20,6 +21,7 @@ on:
       - 'sdk/**'
       - 'sdk-testing/**'
       - 'sdk-integration-tests/**'
+      - 'otel-plugin/**'
       - 'examples/**'
       - 'pom.xml'