stop git-checkout from reverting connections.env on down

toggle_index ran git checkout on connections.env whenever going
down, discarding whatever set_local_db had just written and
restoring whatever format happens to be committed. This silently
undid the RCC_/legacy dual-format toggle. update-index still marks
the file assume-unchanged/no-assume-unchanged; the checkout is gone.

src/git/command.rs

@@ -20,12 +20,5 @@ pub fn toggle_index(start: bool, config: &DevToolsConf) -> Result<()> {
         .args(["update-index", change, &project_path])
         .status()?;
 
-    if !start {
-        Command::new("git")
-            .current_dir(config.project_dir_as_string())
-            .args(["checkout", &project_path])
-            .status()?;
-    }
-
     Ok(())
 }