Bump com.github.johnrengelman.shadow

Bumps com.github.johnrengelman.shadow from 5.1.0 to 8.1.1.

---
updated-dependencies:
- dependency-name: com.github.johnrengelman.shadow
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

samples/lambda-kotlin-request-router-sample-proto/build.gradle.kts

@@ -18,7 +18,7 @@ plugins {
     java
     kotlin("jvm") version "1.3.50"
     idea
-    id("com.github.johnrengelman.shadow") version "5.1.0"
+    id("com.github.johnrengelman.shadow") version "8.1.1"
     id("org.jmailen.kotlinter") version "1.22.0"
     id("com.google.protobuf") version "0.8.7"
 }