Upgrade to Reactor 2020.0.4

Closes spring-projectsgh-26548

Author: rstoyanchev

build.gradle

@@ -28,7 +28,7 @@ configure(allprojects) { project ->
 		imports {
 			mavenBom "com.fasterxml.jackson:jackson-bom:2.12.1"
 			mavenBom "io.netty:netty-bom:4.1.59.Final"
-			mavenBom "io.projectreactor:reactor-bom:2020.0.3"
+			mavenBom "io.projectreactor:reactor-bom:2020.0.4"
 			mavenBom "io.r2dbc:r2dbc-bom:Arabba-SR8"
 			mavenBom "io.rsocket:rsocket-bom:1.1.0"
 			mavenBom "org.eclipse.jetty:jetty-bom:9.4.36.v20210114"