Bump nexus-staging-maven-plugin to 1.7.0 also inside core/

Summary: This follows up the bump for nexus-staging-maven-plugin to 1.7.0

Reviewed By: hick209

Differential Revision: D61846862

fbshipit-source-id: ae83b0eac4c6c66a02bed7a4c194be1669a1a1d1

core/pom.xml

@@ -220,7 +220,7 @@
                     <plugin>
                         <groupId>org.sonatype.plugins</groupId>
                         <artifactId>nexus-staging-maven-plugin</artifactId>
-                        <version>1.6.13</version>
+                        <version>1.7.0</version>
                         <extensions>true</extensions>
                         <configuration>
                             <serverId>ossrh</serverId>