Upgrade Maven surefire plugin to 2.21.0

Closes gh-12721

Author: SteKoe

spring-boot-project/spring-boot-dependencies/pom.xml

@@ -202,7 +202,7 @@
 		<maven-shade-plugin.version>2.4.3</maven-shade-plugin.version>
 		<maven-site-plugin.version>3.6</maven-site-plugin.version>
 		<maven-source-plugin.version>3.0.1</maven-source-plugin.version>
-		<maven-surefire-plugin.version>2.20.1</maven-surefire-plugin.version>
+		<maven-surefire-plugin.version>2.21.0</maven-surefire-plugin.version>
 		<maven-war-plugin.version>3.1.0</maven-war-plugin.version>
 		<versions-maven-plugin.version>2.3</versions-maven-plugin.version>
 		<xml-maven-plugin.version>1.0.1</xml-maven-plugin.version>