Use git config --global user.email for email address in automatic Co-authored-by (#32624)

Release Notes:

- Automatic population of `Co-authored-by` now uses `git config --global
user.email`

---------

Co-authored-by: Conrad Irwin <conrad.irwin@gmail.com>
Co-authored-by: Conrad <conrad@zed.dev>

crates/collab_ui/src/chat_panel.rs

@@ -1218,7 +1218,6 @@ mod tests {
                 avatar_uri: "avatar_fgh".into(),
                 id: 103,
                 name: None,
-                email: None,
             }),
             nonce: 5,
             mentions: vec![(ranges[0].clone(), 101), (ranges[1].clone(), 102)],
@@ -1274,7 +1273,6 @@ mod tests {
                 avatar_uri: "avatar_fgh".into(),
                 id: 103,
                 name: None,
-                email: None,
             }),
             nonce: 5,
             mentions: Vec::new(),
@@ -1323,7 +1321,6 @@ mod tests {
                 avatar_uri: "avatar_fgh".into(),
                 id: 103,
                 name: None,
-                email: None,
             }),
             nonce: 5,
             mentions: Vec::new(),