Update Kotlin version to 1.5.10

Author: zsmb13

build.gradle

@@ -1,5 +1,5 @@
 buildscript {
-    ext.kotlin_version = "1.4.30"
+    ext.kotlin_version = "1.5.10"
     repositories {
         google()
         jcenter()

samplekotlin/src/main/java/com/example/chattutorial/ChannelActivity.kt

@@ -49,7 +49,6 @@ class ChannelActivity : AppCompatActivity() {
         messageInputViewModel.bindView(binding.messageInputView, this)
 
         // Step 3 - Let both MessageListHeaderView and MessageInputView know when we open a thread
-        // Note: the observe syntax used here requires Kotlin 1.4
         messageListViewModel.mode.observe(this) { mode ->
             when (mode) {
                 is Thread -> {

samplekotlin/src/main/java/com/example/chattutorial/ChannelActivity2.kt

@@ -50,7 +50,6 @@ class ChannelActivity2 : AppCompatActivity() {
         messageInputViewModel.bindView(binding.messageInputView, this)
 
         // Step 3 - Let both MessageListHeaderView and MessageInputView know when we open a thread
-        // Note: the observe syntax used here requires Kotlin 1.4
         messageListViewModel.mode.observe(this) { mode ->
             when (mode) {
                 is Thread -> {

samplekotlin/src/main/java/com/example/chattutorial/ChannelActivity3.kt

@@ -52,7 +52,6 @@ class ChannelActivity3 : AppCompatActivity() {
         messageInputViewModel.bindView(binding.messageInputView, this)
 
         // Step 3 - Let both MessageListHeaderView and MessageInputView know when we open a thread
-        // Note: the observe syntax used here requires Kotlin 1.4
         messageListViewModel.mode.observe(this) { mode ->
             when (mode) {
                 is Thread -> {

samplekotlin/src/main/java/com/example/chattutorial/ChannelActivity4.kt

@@ -55,7 +55,6 @@ class ChannelActivity4 : AppCompatActivity() {
         messageInputViewModel.bindView(binding.messageInputView, this)
 
         // Step 3 - Let both MessageListHeaderView and MessageInputView know when we open a thread
-        // Note: the observe syntax used here requires Kotlin 1.4
         messageListViewModel.mode.observe(this) { mode ->
             when (mode) {
                 is Thread -> {

samplekotlin/src/main/java/com/example/chattutorial/MainActivity.kt

@@ -52,7 +52,6 @@ class MainActivity : AppCompatActivity() {
 
         // Step 4 - Connect the ChannelListViewModel to the ChannelListView, loose
         //          coupling makes it easy to customize
-        // Note: the listener syntax used here requires Kotlin 1.4
         viewModel.bindView(binding.channelListView, this)
         binding.channelListView.setChannelItemClickListener { channel ->
             startActivity(ChannelActivity4.newIntent(this, channel))