Bump io.opentelemetry.proto:opentelemetry-proto

Bumps [io.opentelemetry.proto:opentelemetry-proto](https://github.com/open-telemetry/opentelemetry-proto-java) from 1.7.0-alpha to 1.8.0-alpha.
- [Release notes](https://github.com/open-telemetry/opentelemetry-proto-java/releases)
- [Commits](https://github.com/open-telemetry/opentelemetry-proto-java/commits)

---
updated-dependencies:
- dependency-name: io.opentelemetry.proto:opentelemetry-proto
  dependency-version: 1.8.0-alpha
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

smoke-tests/framework/build.gradle.kts

@@ -19,7 +19,7 @@ dependencies {
   implementation("org.eclipse.jetty:jetty-servlet:10.0.26")
 
   implementation("org.mock-server:mockserver-netty:5.15.0:shaded")
-  implementation("io.opentelemetry.proto:opentelemetry-proto:1.7.0-alpha")
+  implementation("io.opentelemetry.proto:opentelemetry-proto:1.8.0-alpha")
 
   // this is exposed in SmokeTestExtension API
   api("org.testcontainers:testcontainers:1.21.3")