docs: Cleanup installation process for Queue Processor

[botchk]

Issue #, if available:

Description of changes:
While going over the installation process for a test setup I noticed some small QoL changes.

• Remove the leading $ for code blocks, makes them functional when copy pasting them to a terminal
• Remove invalid "SqsManagedSseEnabled": true from the queue attributes
  • When executing sqs create-queue this returns the error: Invalid type for parameter Attributes.SqsManagedSseEnabled, value: True, type: <class 'bool'>, valid types: <class 'str'>
  • According to https://docs.aws.amazon.com/AWSSimpleQueueService/latest/SQSDeveloperGuide/sqs-configure-sse-existing-queue.html encryption is enabled by default anyway. Also details on SQS encryption are outlined below the code block.

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[cjerad]

Hi! Thanks for the contribution. To keep the doc formatting consistent please also remove the leading $ from command blocks in BUILD.md

[botchk]

I've removed the $ from BUILD.md as well.

[cjerad]

Thanks for contributing!