Upgrade to Reactor 2020.0.0-M2

Closes gh-25373

Author: rstoyanchev

build.gradle

@@ -25,7 +25,7 @@ configure(allprojects) { project ->
 		imports {
 			mavenBom "com.fasterxml.jackson:jackson-bom:2.11.2"
 			mavenBom "io.netty:netty-bom:4.1.51.Final"
-			mavenBom "io.projectreactor:reactor-bom:2020.0.0-SNAPSHOT"
+			mavenBom "io.projectreactor:reactor-bom:2020.0.0-M2"
 			mavenBom "io.r2dbc:r2dbc-bom:Arabba-SR5"
 			mavenBom "io.rsocket:rsocket-bom:1.1.0-SNAPSHOT"
 			mavenBom "org.eclipse.jetty:jetty-bom:9.4.31.v20200723"
@@ -285,7 +285,8 @@ configure(allprojects) { project ->
 		repositories {
 			mavenCentral()
 			maven { url "https://repo.spring.io/libs-spring-framework-build" }
-			maven { url "https://repo.spring.io/snapshot" } // Reactor and RSocket
+			maven { url "https://repo.spring.io/milestone" } // Reactor
+			maven { url "https://repo.spring.io/snapshot" } // RSocket
 		}
 	}
 	configurations.all {