Use another augmented assignment statement

[elfring]

:eyes: Some source code analysis tools can help to find opportunities for improving software components. :thought_balloon: I propose to increase the usage of augmented assignment statements accordingly.

diff --git a/isort/wrap_modes.py b/isort/wrap_modes.py
index 6ea28018..3e189fd6 100644
--- a/isort/wrap_modes.py
+++ b/isort/wrap_modes.py
@@ -281,7 +281,7 @@ def vertical_prefix_from_module_import(**interface: Any) -> str:
     statement = output_statement
     statement_with_comments = ""
     for next_import in interface["imports"]:
-        statement = statement + ", " + next_import
+        statement += ", " + next_import
         statement_with_comments = isort.comments.add_to_line(
             comments,
             statement,