[ORG] RU-MAKEAPP: 3.x: Update withLatestFrom doc about upstream early complete (#7289)

[sakibguy]

• 3.x: Update withLatestFrom doc about upstream early complete

• Fix singular wording

Thank you for contributing to RxJava. Before pressing the "Create Pull Request" button, please consider the following points:

• Please give a description about what and why you are contributing, even if it's trivial.

• Please include the issue list number(s) or other PR numbers in the description if you are contributing in response to those.

• Please include a reasonable set of unit tests if you contribute new code or change an existing one. If you contribute an operator, (if applicable) please make sure you have tests for working with an empty, just, range of values as well as an error source, with and/or without backpressure and see if unsubscription/cancellation propagates correctly.

[codecov-commenter]

Codecov Report

Merging #28 (4749ab3) into 3.x (91a10d4) will increase coverage by 0.01%.
The diff coverage is n/a.

@@             Coverage Diff              @@
##                3.x      #28      +/-   ##
============================================
+ Coverage     99.51%   99.52%   +0.01%     
+ Complexity     6757     6754       -3     
============================================
  Files           747      747              
  Lines         47391    47391              
  Branches       6382     6382              
============================================
+ Hits          47161    47166       +5     
+ Misses          105      100       -5     
  Partials        125      125              

Impacted Files	Coverage Δ
.../main/java/io/reactivex/rxjava3/core/Flowable.java	100.00% <ø> (ø)
...ain/java/io/reactivex/rxjava3/core/Observable.java	100.00% <ø> (ø)
.../operators/observable/ObservableFlatMapSingle.java	94.44% <0.00%> (-3.18%)	⬇️
...va/io/reactivex/rxjava3/subjects/AsyncSubject.java	97.87% <0.00%> (-2.13%)	⬇️
...o/reactivex/rxjava3/processors/AsyncProcessor.java	97.91% <0.00%> (-2.09%)	⬇️
...reactivex/rxjava3/processors/PublishProcessor.java	98.16% <0.00%> (-1.84%)	⬇️
...nternal/operators/observable/ObservableWindow.java	98.21% <0.00%> (-1.79%)	⬇️
...nternal/operators/parallel/ParallelSortedJoin.java	98.49% <0.00%> (-1.51%)	⬇️
...ators/observable/ObservableFlatMapCompletable.java	98.52% <0.00%> (-1.48%)	⬇️
...ternal/operators/completable/CompletableMerge.java	97.29% <0.00%> (-1.36%)	⬇️
... and 15 more

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[sakibguy]

good work