[Minor] [ML] [Doc] Remove duplicated periods at the end of some sharedParam

[yanboliang]

What changes were proposed in this pull request?

Remove duplicated periods at the end of some sharedParams in ScalaDoc, such as here
cc @mengxr @srowen

How was this patch tested?

Documents change, no test.

[srowen]

@yanboliang this isn't worth changing. The period isn't hurting anything

[SparkQA]

Test build #51870 has finished for PR 11344 at commit a12b1ac.

• This patch fails SparkR unit tests.
• This patch merges cleanly.
• This patch adds the following public classes (experimental):
  • final val thresholds: DoubleArrayParam = new DoubleArrayParam(this, \"thresholds\", \"Thresholds in multi-class classification to adjust the probability of predicting each class. Array must have length equal to the number of classes, with values >= 0. The class with largest value p/t is predicted, where p is the original probability of that class and t is the class' threshold\", (t: Array[Double]) => t.forall(_ >= 0))

[yanboliang]

@srowen Some ScalaDocs will end with two periods if we don't fix, you can refer here.

[SparkQA]

Test build #51881 has finished for PR 11344 at commit a12b1ac.

• This patch fails SparkR unit tests.
• This patch merges cleanly.
• This patch adds the following public classes (experimental):
  • final val thresholds: DoubleArrayParam = new DoubleArrayParam(this, \"thresholds\", \"Thresholds in multi-class classification to adjust the probability of predicting each class. Array must have length equal to the number of classes, with values >= 0. The class with largest value p/t is predicted, where p is the original probability of that class and t is the class' threshold\", (t: Array[Double]) => t.forall(_ >= 0))

[yanboliang]

Jenkins, test this please.

[SparkQA]

Test build #51970 has finished for PR 11344 at commit a12b1ac.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds the following public classes (experimental):
  • final val thresholds: DoubleArrayParam = new DoubleArrayParam(this, \"thresholds\", \"Thresholds in multi-class classification to adjust the probability of predicting each class. Array must have length equal to the number of classes, with values >= 0. The class with largest value p/t is predicted, where p is the original probability of that class and t is the class' threshold\", (t: Array[Double]) => t.forall(_ >= 0))

[jkbradley]

May not be worth it, but I think it's fine to fix. LGTM I'll merge this with master