Python: Improve taint steps in for & iterable unpacking

These were written way before the ones in DataFlowPrivate, but
apparently didn't cover quite as much :|

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

@@ -55,7 +55,7 @@ async def test_taint(request: web.Request): # $ requestHandler
         await request.content.readline(), # $ tainted
         await request.content.readchunk(), # $ tainted
         (await request.content.readchunk())[0], # $ tainted
-        [line async for line in request.content], # $ MISSING: tainted
+        [line async for line in request.content], # $ tainted
         [data async for data in request.content.iter_chunked(1024)], # $ MISSING: tainted
         [data async for data in request.content.iter_any()], # $ MISSING: tainted
         [data async for data, _ in request.content.iter_chunks()], # $ MISSING: tainted

python/ql/test/library-tests/frameworks/django-v2-v3/taint_test.py

@@ -108,7 +108,7 @@ def test_taint(request: HttpRequest, foo, bar, baz=None):  # $requestHandler rou
         request.readline(), # $ tainted
         request.readlines(), # $ tainted
         request.readlines()[0], # $ tainted
-        [line for line in request], # $ MISSING: tainted
+        [line for line in request], # $ tainted
     )
 
     # django.urls.ResolverMatch also supports iterable unpacking

python/ql/test/library-tests/frameworks/tornado/taint_test.py

@@ -63,7 +63,7 @@ class TaintTest(tornado.web.RequestHandler):
             request.headers["header-name"], # $ tainted
             request.headers.get_list("header-name"), # $ tainted
             request.headers.get_all(), # $ tainted
-            [(k, v) for (k, v) in request.headers.get_all()], # $ MISSING: tainted
+            [(k, v) for (k, v) in request.headers.get_all()], # $ tainted
 
             # Dict[str, http.cookies.Morsel]
             request.cookies, # $ tainted