Fix release instructions

Author: vlsi

README.md

@@ -58,11 +58,7 @@ To commit updates to version in `pom.xml` files and create a tag, issue:
 
 To stage the version to maven central, issue:
 
-    mvn release:release
-
-As staging completes, close staging repository (you need to take staging repository id from `release:release` step):
-
-    mvn nexus-staging:close -DstagingRepositoryId=orgpostgresql-1082
+    mvn release:perform
 
 This will open staging repository for smoke testing access at https://oss.sonatype.org/content/repositories/orgpostgresql-1082/