fix: resolve ruff linting issues (E501, E731)

Author: Rohan-Gautam

sorts/sleep_sort.py

@@ -29,10 +29,10 @@ def sleeper(value: int) -> None:
         result.append(value)
 
     threads = [threading.Thread(target=sleeper, args=(x,)) for x in arr]
-    for t in threads:
-        t.start()
-    for t in threads:
-        t.join()
+    for thread in threads:
+        thread.start()
+    for thread in threads:
+        thread.join()
 
     return result