Update react/promise (v2.7.1 => v2.8.0)

[phil-davis]

Description

composer update
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Updating dependencies (including require-dev)
Package operations: 0 installs, 2 updates, 0 removals
  - Updating react/promise (v2.7.1 => v2.8.0): Downloading (100%) 

https://github.com/reactphp/promise/releases/tag/v2.8.0

How Has This Been Tested?

CI

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Database schema changes (next release will require increase of minor version instead of patch)
• Breaking change (fix or feature that would cause existing functionality to change)
• Technical debt
• Tests only (no source changes)

Checklist:

• Code changes
• Unit tests added
• Acceptance tests added
• Documentation ticket raised:
• Changelog item, see TEMPLATE