Remove FIFO queues

[npalm]

Problem

From creation of the module we have offered the ussages of FIFO queues. By default, they are disabled today. The reason for using FIFO is to process messages for repo level in order. THis to ensure scaling happens in a fair order. However, to ensure messages are handled in the right order the 'Message group id` needs to be set.

The webhook lambda is setting this GitHub message id. Meaning the message group is set always unique and the feature had never worked as intended. An obvious solution is set the group id properly.

But since the FIFO queues had never worked as intended the proposal would be a breaking change and remove the FIFO queues completly from the module. Since it had never worked, zero issues are raised and it is useless complexity to maintain.

Solution

Remove all FIFO logic from lambda and terraform. Change should trigger a major release.