Update service limits for email attachments to be more accurate

[apattath]

The email attachment size limits apply not just to attachments, but to the entire email request size. Clarified that in the documentation.

[prmerger-automator[bot]]

@apattath : Thanks for your contribution! The author(s) have been notified to review your proposed change.

[opbld33]

Learn Build status updates of commit 0b48ece:

:white_check_mark: Validation status: passed

File	Status	Preview URL	Details
articles/communication-services/concepts/service-limits.md	:white_check_mark:Succeeded

For more details, please refer to the build report.

Note: Broken links written as relative paths are included in the above build report. For broken links written as absolute paths or external URLs, see the broken link report.

For any questions, please:

• Try searching the learn.microsoft.com contributor guides
• Post your question in the Learn support channel

[Jak-MS]

@tophpalmer

• Can you review this PR?
• IMPORTANT: When this content is ready to merge, you must add #sign-off in a comment or the approval may get overlooked.

#label:"aq-pr-triaged" @MicrosoftDocs/public-repo-pr-review-team

[bashan-git]

#sign-off

[prmerger-automator[bot]]

Invalid command: '#sign-off'. Only the assigned author of one or more file in this PR can sign off. @tophpalmer

[Jak-MS]

Hi @bashan-git

PRMerger will only accept sign off from the listed 'author'. However, if you are a Microsoft employee authorized to update this content, you can send a request to [email protected] for this PR to be merged. Include your role, and an explanation of why the PR should be merged without approval from the listed author.

[tophpalmer]

#sign-off