duration_suboptimal_units: print the complete method name in the suggestion

[ada4a]

changelog: [duration_suboptimal_units]: print the complete method name in the suggestion

[rustbot]

r? @llogiq

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The reviewer was selected based on:

• Owners of files modified in this PR: 7 candidates
• 7 candidates expanded to 7 candidates
• Random selection from Jarcho, llogiq, samueltardieu

[ada4a]

Let's block this until #16922 is merged, to avoid churn for its author

@rustbot blocked