Upgrade to Jetty 9.4.28.v20200408

Closes gh-21193

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

@@ -125,7 +125,7 @@
 		<jedis.version>3.1.0</jedis.version>
 		<jersey.version>2.29.1</jersey.version>
 		<jest.version>6.3.1</jest.version>
-		<jetty.version>9.4.27.v20200227</jetty.version>
+		<jetty.version>9.4.28.v20200408</jetty.version>
 		<jetty-jsp.version>2.2.0.v201112011158</jetty-jsp.version>
 		<jetty-el.version>8.5.49</jetty-el.version>
 		<jetty-reactive-httpclient.version>1.0.3</jetty-reactive-httpclient.version>