Fix the log4j2.isWebapp property naming

Co-authored-by: Piotr P. Karwasz <[email protected]>

Author: vy

log4j-core-test/src/test/java/org/apache/logging/log4j/core/ShutdownDisabledTest.java

@@ -26,7 +26,7 @@
 import org.apache.logging.log4j.test.junit.SetTestProperty;
 import org.junit.jupiter.api.Test;
 
-@SetTestProperty(key = "log4j2.is.webapp", value = "false")
+@SetTestProperty(key = "log4j2.isWebapp", value = "false")
 @LoggerContextSource("log4j-test3.xml")
 class ShutdownDisabledTest {