Python: Fix test to use async with

It doesn't work if just using plain `with`

Author: RasmusWL

python/ql/test/library-tests/frameworks/aiohttp/client_request.py

@@ -6,9 +6,9 @@ async def test():
     resp = await s.request("method", "url") # $ clientRequestUrlPart="url"
     resp = await s.request("method", url="url") # $ clientRequestUrlPart="url"
 
-    with aiohttp.ClientSession() as session:
-        resp = await session.get("url") # $ clientRequestUrlPart="url"
-        resp = await session.request(method="GET", url="url") # $ clientRequestUrlPart="url"
+    async with aiohttp.ClientSession() as session:
+        resp = await session.get("url") # $ MISSING: clientRequestUrlPart="url"
+        resp = await session.request(method="GET", url="url") # $ MISSING: clientRequestUrlPart="url"
 
     # other methods than GET
     s = aiohttp.ClientSession()