Update reactive streams JAR version (#2744)

Fixes #2740
diff --git a/gradle.properties b/gradle.properties
index 5fbf332..a65c816 100644
--- a/gradle.properties
+++ b/gradle.properties
@@ -17,7 +17,7 @@
 dokka_version=0.9.16-rdev-2-mpp-hacks
 byte_buddy_version=1.10.9
 reactor_version=3.4.1
-reactive_streams_version=1.0.2
+reactive_streams_version=1.0.3
 rxjava2_version=2.2.8
 rxjava3_version=3.0.2
 javafx_version=11.0.2