Set release branch version to 0.9.0 (#1766)

Author: Anuraag Agrawal

build.gradle

@@ -13,7 +13,7 @@ ext {
 
 subprojects {
     group = "io.opentelemetry"
-    version = "0.9.1-SNAPSHOT" // CURRENT_OPEN_TELEMETRY_VERSION
+    version = "0.9.0" // CURRENT_OPEN_TELEMETRY_VERSION
 
     plugins.withId("maven-publish") {
         // Always include the artifactory/bintray plugins to do the deployment.