Upgrade to Rxjava2 2.1.12

Closes gh-12617

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

@@ -140,7 +140,7 @@
 		<reactive-streams.version>1.0.2</reactive-streams.version>
 		<rxjava.version>1.3.7</rxjava.version>
 		<rxjava-adapter.version>1.2.1</rxjava-adapter.version>
-		<rxjava2.version>2.1.10</rxjava2.version>
+		<rxjava2.version>2.1.12</rxjava2.version>
 		<selenium.version>3.9.1</selenium.version>
 		<selenium-htmlunit.version>2.29.2</selenium-htmlunit.version>
 		<sendgrid.version>4.1.2</sendgrid.version>