Fix markdown formatting in network_container.html.markdown

[pmacey]

Description

Noticed that the markdown rendering was incorrect for the network container documentation, specifically where delimiting the cloud provider attributes references.

Type of change:

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update
• Documentation fix/enhancement

Required Checklist:

• I have signed the MongoDB CLA
• I have read the Terraform contribution guidelines
• I have added tests that prove my fix is effective or that my feature works per HashiCorp requirements
• I have added any necessary documentation (if appropriate)
• I have run make fmt and formatted my code

Further comments

To avoid noise, I did not create an issue for this minor change, happy to do so if required.

[themantissa]

Thank you for the fix @pmacey.