fix team memberships

Author: pietroalbini

posts/inside-rust/2020-02-27-pietro-joins-core-team.md

@@ -7,7 +7,7 @@ team: the core team <https://www.rust-lang.org/governance/teams/core>
 
 We are very happy to announce that [Pietro Albini](https://github.com/pietroalbini) has joined the core team. Pietro joined us back on December 24th 2019 (a Christmas present for the core team!), but we have been a bit late in announcing it (sorry Pietro!).
 
-Pietro co-leads of the infrastructure and docs.rs teams, and is a member of the crates.io and release teams, and the security response working groups. He has been instrumental in setting up and maintaining the various services and technology which keeps the Rust project moving quickly and smoothly.
+Pietro co-leads the infrastructure and docs.rs teams, and is a member of the crates.io and release teams, and the security response working group. He has been instrumental in setting up and maintaining the various services and technology which keeps the Rust project moving quickly and smoothly.
 
 Pietro will continue to focus on infrastructure issues, starting with setting up a team to coordinate Rust's web presence - the website, crates.io, docs.rs, etc.