remove exception, messager and add comment

libraries/apollo-compiler/src/main/kotlin/com/apollographql/apollo3/compiler/ApolloCompilerPluginLogger.kt

@@ -13,6 +13,4 @@ interface ApolloCompilerPluginLogger {
   fun info(message: String)
   fun warn(message: String)
   fun error(message: String)
-
-  fun exception(e: Throwable)
 }

libraries/apollo-compiler/src/main/kotlin/com/apollographql/apollo3/compiler/internal/GradleCompilerPluginLogger.kt

@@ -5,34 +5,32 @@ import com.apollographql.apollo3.compiler.ApolloCompilerPluginLogger
 
 @ApolloInternal
 class GradleCompilerPluginLogger(val loglevel: Int) : ApolloCompilerPluginLogger {
-  private val messager = System.out
 
   override fun logging(message: String) {
     if (loglevel <= LOGGING_LEVEL_LOGGING)
-      messager.println("v: [apollo] $message")
+      println("v: [apollo] $message")
   }
 
   override fun info(message: String) {
     if (loglevel <= LOGGING_LEVEL_INFO)
-      messager.println("i: [apollo] $message")
+      println("i: [apollo] $message")
   }
 
   override fun warn(message: String) {
     if (loglevel <= LOGGING_LEVEL_WARN)
-      messager.println("w: [apollo] $message")
+      println("w: [apollo] $message")
   }
 
   override fun error(message: String) {
     if (loglevel <= LOGGING_LEVEL_ERROR)
-      messager.println("e: [apollo] $message")
-  }
-
-  override fun exception(e: Throwable) {
-    if (loglevel <= LOGGING_LEVEL_ERROR)
-      messager.println("e: [apollo] $e")
+      println("e: [apollo] $message")
   }
 
   companion object {
+    /**
+     * Matches Gradle LogLevel
+     * See https://github.com/gradle/gradle/blob/71f42531a742bc263c61f1d0dc21bb6570cc817b/platforms/core-runtime/logging-api/src/main/java/org/gradle/api/logging/LogLevel.java#L21
+     */
     const val LOGGING_LEVEL_LOGGING = 0
     const val LOGGING_LEVEL_INFO = 1
     const val LOGGING_LEVEL_WARN = 3