3.x: Remove fromFuture(..., Scheduler) overloads

[akarnokd]

Those overloads were only applying subscribeOn with no other benefits.

Resolves: #6811

[codecov]

Codecov Report

Merging #6814 into 3.x will increase coverage by 0.02%.
The diff coverage is n/a.

@@             Coverage Diff              @@
##                3.x    #6814      +/-   ##
============================================
+ Coverage     98.26%   98.28%   +0.02%     
+ Complexity     6385     6378       -7     
============================================
  Files           715      715              
  Lines         46498    46486      -12     
  Branches       6371     6371              
============================================
- Hits          45689    45687       -2     
+ Misses          284      283       -1     
+ Partials        525      516       -9

Impacted Files	Coverage Δ	Complexity Δ
...rc/main/java/io/reactivex/rxjava3/core/Single.java	100% <ø> (ø)	151 <0> (-2)	⬇️
.../main/java/io/reactivex/rxjava3/core/Flowable.java	100% <ø> (ø)	575 <0> (-2)	⬇️
...ain/java/io/reactivex/rxjava3/core/Observable.java	100% <ø> (ø)	551 <0> (-2)	⬇️
.../operators/observable/ObservableFlatMapSingle.java	88.88% <0%> (-6.35%)	2% <0%> (ø)
...eactivex/rxjava3/processors/BehaviorProcessor.java	96.55% <0%> (-2.47%)	50% <0%> (ø)
...ivex/rxjava3/subscribers/SerializedSubscriber.java	98.86% <0%> (-1.14%)	26% <0%> (-1%)
...a3/internal/operators/flowable/FlowableCreate.java	96.44% <0%> (-0.98%)	6% <0%> (ø)
...rxjava3/internal/schedulers/ExecutorScheduler.java	95.89% <0%> (-0.92%)	10% <0%> (ø)
...3/internal/operators/flowable/FlowableGroupBy.java	95.59% <0%> (-0.63%)	3% <0%> (ø)
.../reactivex/rxjava3/observers/BaseTestConsumer.java	96.68% <0%> (-0.56%)	68% <0%> (-1%)
... and 13 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 45c0b06...f4f0138. Read the comment docs.