Update dependency io.opentelemetry.proto:opentelemetry-proto to v1.3.1-alpha (#403)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

telemetry-testing/build.gradle.kts

@@ -39,7 +39,7 @@ dependencies {
     testImplementation("org.junit.jupiter:junit-jupiter-engine")
     testImplementation("org.mock-server:mockserver-netty:5.15.0:shaded")
     testImplementation("org.awaitility:awaitility:4.2.1")
-    testImplementation("io.opentelemetry.proto:opentelemetry-proto:1.2.0-alpha")
+    testImplementation("io.opentelemetry.proto:opentelemetry-proto:1.3.1-alpha")
     testImplementation("org.assertj:assertj-core:3.25.3")
 
     agent("io.opentelemetry.javaagent:opentelemetry-javaagent:2.3.0")