Downgrade spring-boot-starter-parent version

Signed-off-by: Pekka Helenius <fincer89@hotmail.com>

exercises/chapter_0/chapter0_helloworld/pom.xml

@@ -5,7 +5,7 @@
 	<parent>
 		<groupId>org.springframework.boot</groupId>
 		<artifactId>spring-boot-starter-parent</artifactId>
-		<version>2.3.3.RELEASE</version>
+		<version>2.2.4.RELEASE</version>
 		<relativePath/> <!-- lookup parent from repository -->
 	</parent>
 	<groupId>com.fjordtek</groupId>

exercises/chapter_1/chapter1_httprequest/pom.xml

@@ -5,7 +5,7 @@
 	<parent>
 		<groupId>org.springframework.boot</groupId>
 		<artifactId>spring-boot-starter-parent</artifactId>
-		<version>2.3.3.RELEASE</version>
+		<version>2.2.4.RELEASE</version>
 		<relativePath/> <!-- lookup parent from repository -->
 	</parent>
 	<groupId>com.fjordtek</groupId>