Bump org.slf4j:slf4j-simple from 1.7.21 to 2.0.13

Bumps org.slf4j:slf4j-simple from 1.7.21 to 2.0.13.

---
updated-dependencies:
- dependency-name: org.slf4j:slf4j-simple
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

build.gradle

@@ -112,7 +112,7 @@ dependencies {
     compile "org.slf4j:slf4j-api:2.0.13"
     // Specific slf4j bindings should not be included in the default (compile) scope.
     // See http://www.slf4j.org/faq.html#maven2.
-    testCompile "org.slf4j:slf4j-simple:1.7.21"
+    testCompile "org.slf4j:slf4j-simple:2.0.13"
     compile "io.grpc:grpc-protobuf:${grpcVersion}"
     compile "io.grpc:grpc-netty:${grpcVersion}"
     compile "io.grpc:grpc-stub:${grpcVersion}"