Update maven war plugin

Author: AB-xdev

vaadin-date-range-picker-demo/pom.xml

@@ -102,6 +102,14 @@
 					<release>${maven.compiler.release}</release>
 				</configuration>
 			</plugin>
+			<plugin>
+				<groupId>org.apache.maven.plugins</groupId>
+				<artifactId>maven-war-plugin</artifactId>
+				<version>3.3.1</version>
+				<configuration>
+					<failOnMissingWebXml>false</failOnMissingWebXml>
+				</configuration>
+			</plugin>
 		</plugins>
 	</build>