docs: Use code format for env variables in upgrade guide

[bbodenmiller]

Fixes #N/A

Description

Use code format for env variables in upgrade guide

How was this change tested?

n/a

Does this change impact docs?

• Yes, PR includes docs updates
• Yes, issue opened: #
• No

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

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[jonathan-innis]

LGTM 🚀

[jonathan-innis]

@bbodenmiller I approved but it looks like this needs a rebase now

[coveralls]

Pull Request Test Coverage Report for Build 11937163368

Warning: This coverage report may be inaccurate.

This pull request's base commit is no longer the HEAD commit of its target branch. This means it includes changes from outside the original pull request, including, potentially, unrelated coverage changes.

• For more information on this, see Tracking coverage changes with pull request builds.
• To avoid this issue with future PRs, see these Recommended CI Configurations.
• For a quick fix, rebase this PR at GitHub. Your next report should be accurate.

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 82.449%

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Totals
Change from base Build 11924046371:	0.0%
Covered Lines:	5684
Relevant Lines:	6894

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💛 - Coveralls