Update the copyright notices to the new requirements (#4016)

* Remove copyright notices from individual files;
* Update the NOTICE file to include the year of initial publication
  and the year of the latest change;
* Remove the IDEA template for adding notices to every file.

This is in accordance with
https://youtrack.jetbrains.com/articles/MKT-A-236159528/, using the
clarifications from
https://youtrack.jetbrains.com/issue/LegalCZ-6871

Author: dkhalanskyjb

.idea/copyright/kotlinx_coroutines.xml

@@ -1,7 +1,3 @@
-/*
- * Copyright 2016-2023 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license.
- */
-
 @file:Suppress("UnstableApiUsage")
 
 import org.jetbrains.kotlin.gradle.tasks.*

benchmarks/build.gradle.kts

@@ -1,7 +1,3 @@
-/*
- * Copyright 2016-2021 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license.
- */
-
 package benchmarks.flow.scrabble;
 
 import benchmarks.flow.scrabble.IterableSpliterator;

benchmarks/src/jmh/java/benchmarks/flow/scrabble/RxJava2PlaysScrabble.java

@@ -1,7 +1,3 @@
-/*
- * Copyright 2016-2021 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license.
- */
-
 package benchmarks.flow.scrabble;
 
 import java.util.*;

benchmarks/src/jmh/java/benchmarks/flow/scrabble/RxJava2PlaysScrabbleOpt.java

@@ -1,7 +1,3 @@
-/*
- * Copyright 2016-2021 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license.
- */
-
 package benchmarks.flow.scrabble.optimizations;
 
 import io.reactivex.Flowable;

benchmarks/src/jmh/java/benchmarks/flow/scrabble/optimizations/FlowableCharSequence.java

@@ -1,7 +1,3 @@
-/*
- * Copyright 2016-2021 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license.
- */
-
 package benchmarks.flow.scrabble.optimizations;
 
 import io.reactivex.Flowable;

benchmarks/src/jmh/java/benchmarks/flow/scrabble/optimizations/FlowableSplit.java

@@ -1,7 +1,3 @@
-/*
- * Copyright 2016-2021 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license.
- */
-
 package benchmarks.flow.scrabble.optimizations;
 
 import io.reactivex.Flowable;

benchmarks/src/jmh/java/benchmarks/flow/scrabble/optimizations/StringFlowable.java

@@ -1,7 +1,3 @@
-/*
- * Copyright 2016-2021 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license.
- */
-
 package benchmarks
 
 import kotlinx.coroutines.*

benchmarks/src/jmh/kotlin/benchmarks/ChannelSinkBenchmark.kt

@@ -1,7 +1,3 @@
-/*
- * Copyright 2016-2021 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license.
- */
-
 package benchmarks
 
 import kotlinx.coroutines.*

benchmarks/src/jmh/kotlin/benchmarks/ChannelSinkDepthBenchmark.kt

@@ -1,7 +1,3 @@
-/*
- * Copyright 2016-2023 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license.
- */
-
 package benchmarks
 
 import kotlinx.coroutines.*