Removed references to spark.shuffle.service.enabled = true

[ChrisSoderberg-ONS]

Merge request template: please remove the appropriate parts of this template.

Pre-merge request checklist (to be completed by the one making the request):

• I have performed a full review of this code myself.
  • For Python code in PySpark specific sections, all code should have been run in Jupyter notebooks.
  • For code in sections of the book containing both Python and R code, the page of the book should be constructed as described in the contributing guide and converted to a markdown file.
• I have formatted the outputs of code blocks correctly (to match other outputs in the book and in line with the style guide [coming soon])
• I have built the book as outlined in the contributing guide and confirmed that any additional/modified content is displaying as expected.

Details of this request (such as):

• Removed references to spark.shuffle.service.enabled = true due to complaints from users as this configuration must be disabled when using Spark on Cloudera Machine Learning

Requirements for review (such as):

• Review markdown edits
• Build book

[emercado4]

Thanks Chris, changes made all look good and I can't find any other references to spark.shuffle.service.enabled = true so I think this is ready to merge in.