simplify Build::update_existing_submodule

`Build::update_existing_submodule` is already doing the same thing..

Signed-off-by: onur-ozkan <work@onurozkan.dev>

Author: onur-ozkan

src/bootstrap/src/lib.rs

@@ -545,11 +545,7 @@ impl Build {
             // Look for `submodule.$name.path = $path`
             // Sample output: `submodule.src/rust-installer.path src/tools/rust-installer`
             let submodule = line.split_once(' ').unwrap().1;
-            let path = Path::new(submodule);
-            // Don't update the submodule unless it's already been cloned.
-            if GitInfo::new(false, path).is_managed_git_subrepository() {
-                self.config.update_submodule(submodule);
-            }
+            self.update_existing_submodule(submodule);
         }
     }