Clean up, removed dead code, rename job, documentation tidy up

[mockitoguy]

• Removed dead method to simplify the code
• Renamed iOngoingStubbing -> ongoingStubbing ('i' prefix is a relict of history)
• Removed duplicated word (thanks to @kant for inspiration in Duplicated word on #66 #1288)

[codecov-io]

Codecov Report

Merging #1290 into release/2.x will decrease coverage by <.01%.
The diff coverage is 50%.

@@                Coverage Diff                @@
##             release/2.x    #1290      +/-   ##
=================================================
- Coverage          88.08%   88.07%   -0.01%     
+ Complexity          2321     2320       -1     
=================================================
  Files                284      284              
  Lines               5857     5855       -2     
  Branches             702      702              
=================================================
- Hits                5159     5157       -2     
  Misses               519      519              
  Partials             179      179

Impacted Files	Coverage Δ	Complexity Δ
...ito/internal/stubbing/InvocationContainerImpl.java	92.85% <ø> (-0.25%)	28 <0> (-1)
...mockito/internal/progress/MockingProgressImpl.java	97.26% <50%> (ø)	29 <1> (ø)	⬇️

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