Contributing: fix a typo

[MaherJendoubi]

Fixing a typo:

• Fix typo in the comments of Dispose methods.

[codecov]

Codecov Report

Merging #4617 into master will increase coverage by 0.75%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #4617      +/-   ##
==========================================
+ Coverage   74.88%   75.64%   +0.75%     
==========================================
  Files         935      938       +3     
  Lines      168440   168623     +183     
  Branches    18189    18206      +17     
==========================================
+ Hits       126132   127550    +1418     
+ Misses      37325    36038    -1287     
- Partials     4983     5035      +52

Flag	Coverage Δ
#Debug	75.64% <ø> (+0.75%)	⬆️
#production	71.26% <ø> (+0.99%)	⬆️
#test	90.43% <ø> (ø)	⬆️

Impacted Files	Coverage Δ
.../Microsoft.ML.Vision/ImageClassificationTrainer.cs	91.06% <ø> (+6.55%)	⬆️
....ML.AutoML/PipelineSuggesters/PipelineSuggester.cs	83.19% <0%> (-3.37%)	⬇️
...rosoft.ML.AutoML/ColumnInference/TextFileSample.cs	59.6% <0%> (-2.65%)	⬇️
...L.AutoML/TrainerExtensions/TrainerExtensionUtil.cs	85.15% <0%> (-1.75%)	⬇️
src/Microsoft.ML.AutoML/Sweepers/Parameters.cs	84.32% <0%> (-0.85%)	⬇️
src/Microsoft.ML.Transforms/Text/LdaTransform.cs	84.44% <0%> (-0.16%)	⬇️
....Experimental/OneToOneTransformerBaseExtensions.cs	100% <0%> (ø)
...c/Microsoft.ML.Experimental/MLContextExtensions.cs	0% <0%> (ø)
...c/Microsoft.ML.SamplesUtils/SamplesDatasetUtils.cs	39.77% <0%> (ø)
...soft.ML.Data/DataLoadSave/Text/TextLoaderCursor.cs	85.31% <0%> (+0.2%)	⬆️
... and 19 more