Bump protobuf-gradle-plugin to 0.8.18 and protoc to 3.21.1

app/build.gradle

@@ -106,7 +106,7 @@ play {
 // per protobuf-gradle-plugin docs, this is recommended for android
 protobuf {
     protoc {
-        artifact = 'com.google.protobuf:protoc:3.15.3'
+        artifact = 'com.google.protobuf:protoc:3.21.1'
     }
     generateProtoTasks {
         all().each { task ->
@@ -160,7 +160,7 @@ dependencies {
     implementation "org.jetbrains.kotlinx:kotlinx-coroutines-android:$coroutines_version"
 
     // For now I'm not using javalite, because I want JSON printing
-    implementation 'com.google.protobuf:protobuf-java:3.15.8'
+    implementation 'com.google.protobuf:protobuf-java:3.21.1'
 
     // For UART access
     // implementation 'com.google.android.things:androidthings:1.0'

build.gradle

@@ -26,7 +26,7 @@ buildscript {
         classpath 'com.google.firebase:firebase-crashlytics-gradle:2.8.1'
 
         // protobuf plugin - docs here https://github.com/google/protobuf-gradle-plugin
-        classpath 'com.google.protobuf:protobuf-gradle-plugin:0.8.17'
+        classpath 'com.google.protobuf:protobuf-gradle-plugin:0.8.18'
 
         //classpath "app.brant:amazonappstorepublisher:0.1.0"
         classpath 'com.github.triplet.gradle:play-publisher:2.8.0'