Docs: Correct grammar error in Message definition (GLOSSARY.md)

[huzaifaalmesbah]

Description

This PR fixes a grammatical error in the glossary documentation.

Changes

• Fixed the Message definition in docs/GLOSSARY.md
• Changed "optionally containing of multiple message parts" to "optionally consisting of multiple message parts"

Rationale

The phrase "containing of" is grammatically incorrect. The correct phrasing is either:

• "consisting of" (used in this fix)
• "containing" (without "of")

Since we want to convey that a message is composed/made up of parts, "consisting of" is the more appropriate choice.

Type of Change

• Documentation fix
• Typo/grammar correction

Checklist

• The change follows the project's coding standards
• Documentation has been updated appropriately
• No tests are needed (documentation-only change)

[github-actions]

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[dhruvang21]

Nice Catch

[felixarntz]

@huzaifaalmesbah Thanks, great catch!