net: rmnet_data: Remove invalid error message

The worker thread can run even if the aggregation state machine
has moved on to an idle after processing packets. This results
in log spam with an invalid message.

CRs-Fixed: 2165883
Change-Id: I218ac9b20a41749adce45a0d787782d15f07c65b
Signed-off-by: Subash Abhinov Kasiviswanathan <subashab@codeaurora.org>