remove sbt-pgp setting in team-rules.md

because

- there is `project/sbt-pgp.sbt` in scalikejdbc repo.
- sbt-pgp version 1.0.0 is does not support sbt 1.x

https://github.com/scalikejdbc/scalikejdbc/blob/2ddee94cc509e12c3451f1962d739828235b0d3d/project/sbt-pgp.sbt

team-rules.md

@@ -58,13 +58,6 @@ If you're already allowed to release ScalikeJDBC libs, use your own Sonatype acc
 credentials += Credentials("Sonatype Nexus Repository Manager", "oss.sonatype.org", "xxx", "yyy")
 ```
 
-- $HOME/.sbt/1.0/plugins/gpg.sbt
-
-```scala
-// Use latest version
-addSbtPlugin("com.jsuereth" % "sbt-pgp" % "1.0.0")
-```
-
 #### Operations
 
 The release manager is @seratch. Currently, all the following operations should be done by @seratch.