[build.gradle] Upgraded to update of the chapter

Chapter2/RssReader/build.gradle

@@ -1,8 +1,8 @@
 // Top-level build file where you can add configuration options common to all sub-projects/modules.
 
 buildscript {
-    ext.kotlin_version = '1.2.21'
-    ext.coroutines_version = '0.21.2'
+    ext.kotlin_version = '1.2.50'
+    ext.coroutines_version = '0.23.3'
 
     repositories {
         google()

Chapter3/RssReader/build.gradle

@@ -1,8 +1,8 @@
 // Top-level build file where you can add configuration options common to all sub-projects/modules.
 
 buildscript {
-    ext.kotlin_version = '1.2.21'
-    ext.coroutines_version = '0.21.2'
+    ext.kotlin_version = '1.2.50'
+    ext.coroutines_version = '0.23.3'
 
     repositories {
         google()

Chapter4/RssReader/build.gradle

@@ -1,8 +1,8 @@
 // Top-level build file where you can add configuration options common to all sub-projects/modules.
 
 buildscript {
-    ext.kotlin_version = '1.2.21'
-    ext.coroutines_version = '0.21.2'
+    ext.kotlin_version = '1.2.50'
+    ext.coroutines_version = '0.23.3'
 
     repositories {
         google()

Chapter5/RssReader/build.gradle

@@ -1,8 +1,8 @@
 // Top-level build file where you can add configuration options common to all sub-projects/modules.
 
 buildscript {
-    ext.kotlin_version = '1.2.30'
-    ext.coroutines_version = '0.21.2'
+    ext.kotlin_version = '1.2.50'
+    ext.coroutines_version = '0.23.3'
 
     repositories {
         google()

Chapter6/RssReader/build.gradle

@@ -1,8 +1,8 @@
 // Top-level build file where you can add configuration options common to all sub-projects/modules.
 
 buildscript {
-    ext.kotlin_version = '1.2.30'
-    ext.coroutines_version = '0.21.2'
+    ext.kotlin_version = '1.2.50'
+    ext.coroutines_version = '0.23.3'
 
     repositories {
         google()

Chapter7/RssReader/build.gradle

@@ -1,8 +1,8 @@
 // Top-level build file where you can add configuration options common to all sub-projects/modules.
 
 buildscript {
-    ext.kotlin_version = '1.2.41'
-    ext.coroutines_version = '0.22.5'
+    ext.kotlin_version = '1.2.50'
+    ext.coroutines_version = '0.23.3'
 
     repositories {
         google()