Remove duplicate slash from resolved WebJar locations

This commit updates the WEBJARS_LOCATION in WebJarResourceResolver to
avoid getting duplicate slashes in resolved resources locations such
as `/webjars//bootstrap/3.3.2/js/bootstrap.min.js`.

Issue: SPR-14018

spring-webmvc/src/main/java/org/springframework/web/servlet/resource/WebJarsResourceResolver.java

@@ -45,7 +45,7 @@ import org.springframework.core.io.Resource;
  */
 public class WebJarsResourceResolver extends AbstractResourceResolver {
 
-	private final static String WEBJARS_LOCATION = "META-INF/resources/webjars";
+	private final static String WEBJARS_LOCATION = "META-INF/resources/webjars/";
 
 	private final static int WEBJARS_LOCATION_LENGTH = WEBJARS_LOCATION.length();