[MLlib][TYPO] Replace LeastSquaresAggregator with LogisticAggregator

[moutai]

What changes were proposed in this pull request?

Replace LeastSquaresAggregator with LogisticAggregator in the require statement of the merge op.

How was this patch tested?

Simple message fix.

[srowen]

Sure, I wonder if there are other similar typos in versions of this message that may be copied and pasted elsewhere? can you take a quick look?

[SparkQA]

Test build #3579 has finished for PR 16903 at commit 669820c.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds no public classes.

[srowen]

(Doesn't look like it, so merged to master)

[moutai]

Thanks,
Yes I think the rest of the messages look fine on this file.