refactor: refactor unnecessary else / elif when if block has a return statement

The use of `else` or `elif` becomes redundant and can be dropped if the last statement under the leading `if` / `elif` block is a `return` statement.
In the case of an `elif` after `return`, it can be written as a separate `if` block.
For `else` blocks after `return`, the statements can be shifted out of `else`. Please refer to the examples below for reference.

Refactoring the code this way can improve code-readability and make it easier to maintain.

onlylegs/app.py

@@ -138,8 +138,7 @@ def handle_errors():
                 render_template("error.html", error=err.code, msg=err.description),
                 err.code,
             )
-        else:
-            return str(err.code) + ": " + err.description, err.code
+        return str(err.code) + ": " + err.description, err.code
 
 
 def register_blueprints():