Update grpc-java monorepo to v1.81.0 (open-telemetry#224)

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

Author: renovate[bot]

build.gradle.kts

@@ -29,7 +29,7 @@ version = ver
 
 description = "Java Bindings for the OpenTelemetry Protocol (OTLP)"
 
-val grpcVersion = "1.80.0"
+val grpcVersion = "1.81.0"
 val protobufVersion = "4.34.1"
 
 repositories {