[DOCS][STREAMING][KAFKA]Fix typo in exactly once semantics

[moutai]

Fix Typo in exactly once semantics
[Semantics of output operations] link

[srowen]

Yeah, that's pretty trivial but OK. (As an aside, yeah I wish this markdown was written with line breaks so the difference would be more obvious.)

[SparkQA]

Test build #1693 has finished for PR 8468 at commit ce3fc00.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds the following public classes (experimental):
  • class LogisticRegressionModel @Since("1.3.0") (
  • class SVMModel @Since("1.1.0") (
  • class GaussianMixtureModel @Since("1.3.0") (
  • class KMeansModel @Since("1.1.0") (@Since("1.0.0") val clusterCenters: Array[Vector])
  • class PowerIterationClusteringModel @Since("1.3.0") (
  • class StreamingKMeansModel @Since("1.2.0") (
  • class StreamingKMeans @Since("1.2.0") (
  • class BinaryClassificationMetrics @Since("1.3.0") (
  • class MulticlassMetrics @Since("1.1.0") (predictionAndLabels: RDD[(Double, Double)])
  • class MultilabelMetrics @Since("1.2.0") (predictionAndLabels: RDD[(Array[Double], Array[Double])])
  • class RegressionMetrics @Since("1.2.0") (
  • class ChiSqSelectorModel @Since("1.3.0") (
  • class ChiSqSelector @Since("1.3.0") (
  • class ElementwiseProduct @Since("1.4.0") (
  • class IDF @Since("1.2.0") (@Since("1.2.0") val minDocFreq: Int)
  • class Normalizer @Since("1.1.0") (p: Double) extends VectorTransformer
  • class PCA @Since("1.4.0") (@Since("1.4.0") val k: Int)
  • class StandardScaler @Since("1.1.0") (withMean: Boolean, withStd: Boolean) extends Logging
  • class StandardScalerModel @Since("1.3.0") (
  • class FPGrowthModel[Item: ClassTag] @Since("1.3.0") (
  • class FreqItemset[Item] @Since("1.3.0") (
  • class FreqSequence[Item] @Since("1.5.0") (
  • class PrefixSpanModel[Item] @Since("1.5.0") (
  • class DenseMatrix @Since("1.3.0") (
  • class SparseMatrix @Since("1.3.0") (
  • class DenseVector @Since("1.0.0") (
  • class SparseVector @Since("1.0.0") (
  • class BlockMatrix @Since("1.3.0") (
  • class CoordinateMatrix @Since("1.0.0") (
  • class IndexedRowMatrix @Since("1.0.0") (
  • class RowMatrix @Since("1.0.0") (
  • class PoissonGenerator @Since("1.1.0") (
  • class ExponentialGenerator @Since("1.3.0") (
  • class GammaGenerator @Since("1.3.0") (
  • class LogNormalGenerator @Since("1.3.0") (
  • abstract class GeneralizedLinearModel @Since("1.0.0") (
  • class IsotonicRegressionModel @Since("1.3.0") (
  • case class LabeledPoint @Since("1.0.0") (
  • class LassoModel @Since("1.1.0") (
  • class LinearRegressionModel @Since("1.1.0") (
  • class RidgeRegressionModel @Since("1.1.0") (
  • class MultivariateGaussian @Since("1.3.0") (
  • case class BoostingStrategy @Since("1.4.0") (
  • class Strategy @Since("1.3.0") (
  • class DecisionTreeModel @Since("1.0.0") (
  • class Node @Since("1.2.0") (
  • class Predict @Since("1.2.0") (
  • class RandomForestModel @Since("1.2.0") (
  • class GradientBoostedTreesModel @Since("1.2.0") (