#5766: Patch generic_multi graph to fix legend overflow

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This should fix issue #5766 by shrinking $desc_len to 12 characters for thiner graphs. That way the Average column doesn't get pushed off the edge of the graph. This

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Thank you for submitting a PR @jquagga! We have found the following @murrant and @paulgear based on the history of these files to review this PR.

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