Simplify gather_requirements implementation

micropip/transaction.py

@@ -48,14 +48,10 @@ async def gather_requirements(
         self,
         requirements: list[str] | list[Requirement],
     ) -> None:
-        requirement_promises = []
-        for requirement in requirements:
-            requirement_promises.append(self.add_requirement(requirement))
-
         futures: list[asyncio.Future] = []
         try:
-            for coro in requirement_promises:
-                futures.append(asyncio.ensure_future(coro))
+            for requirement in requirements:
+                futures.append(asyncio.ensure_future(self.add_requirement(requirement)))
             await asyncio.gather(*futures)
         except ValueError:
             if not self.keep_going: