Update the Javadoc of the retry operator

[RomanWuattier]

Specify that the times function parameter describes "the number of times
to resubscribe if the current Observable fails".

Solves: #6402

[RomanWuattier]

Bellow is the marble with the number of retries decreased from 2 to 1. If the marble is correct, can you upload it to the repository?

[akarnokd]

Sure. Could you also make sure all the other counted retry() operators in the other base classes have the correct wording?

[codecov]

Codecov Report

Merging #6458 into 2.x will decrease coverage by <.01%.
The diff coverage is n/a.

@@             Coverage Diff              @@
##                2.x    #6458      +/-   ##
============================================
- Coverage     98.26%   98.25%   -0.01%     
+ Complexity     6295     6293       -2     
============================================
  Files           675      675              
  Lines         45173    45173              
  Branches       6246     6246              
============================================
- Hits          44387    44386       -1     
- Misses          245      248       +3     
+ Partials        541      539       -2

Impacted Files	Coverage Δ	Complexity Δ
src/main/java/io/reactivex/Flowable.java	100% <ø> (ø)	567 <0> (ø)	⬇️
src/main/java/io/reactivex/Maybe.java	100% <ø> (ø)	173 <0> (ø)	⬇️
src/main/java/io/reactivex/Completable.java	100% <ø> (ø)	120 <0> (ø)	⬇️
src/main/java/io/reactivex/Observable.java	100% <ø> (ø)	542 <0> (ø)	⬇️
...nternal/operators/observable/ObservableCreate.java	96.58% <0%> (-2.57%)	2% <0%> (ø)
...perators/single/SingleFlatMapIterableFlowable.java	95.83% <0%> (-2.5%)	2% <0%> (ø)
...ernal/operators/flowable/FlowableFlatMapMaybe.java	93.71% <0%> (-1.94%)	2% <0%> (ø)
.../io/reactivex/disposables/CompositeDisposable.java	98.14% <0%> (-1.86%)	39% <0%> (-1%)
...java/io/reactivex/processors/UnicastProcessor.java	98.8% <0%> (-1.2%)	67% <0%> (-1%)
...io/reactivex/subscribers/SerializedSubscriber.java	98.86% <0%> (-1.14%)	26% <0%> (-1%)
... and 26 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 3958d1b...d7273d6. Read the comment docs.

[RomanWuattier]

Sure.
I updated every base classes. Also, I grabbed this opportunity to update some unit tests to illustrate the Javadoc wording.

Please, note:

• Single already has the right wording.
• Both Maybe and Flowable are using the default retry marble (https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/retry.png)

[akarnokd]

Nice! Thanks!