docs(sdk-metrics): Update Histogram docs to reflect upper bound inclusivity

[danielpatrickdotdev]

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Which problem is this PR solving?

According to the specs, histogram bucket upper bounds are inclusive. This PR contains a very small change to the docs to reflect that. This might avoid confusing a newcomer to the project.

Fixes # N/A

Short description of the changes

Type of change

Docs only

How Has This Been Tested?

N/A

Checklist:

• [Y] Followed the style guidelines of this project
• [N/A] Unit tests have been added
• [Y] Documentation has been updated