fix autodiff apply, fix a docstring error

[GiggleLiu]

@Roger-luo we need to release a patch fix since a student needs to use this feature for development.

[codecov]

Codecov Report

Patch coverage: 100.00% and no project coverage change.

Comparison is base (b971dd4) 88.88% compared to head (44d410f) 88.88%.
Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #478   +/-   ##
=======================================
  Coverage   88.88%   88.88%           
=======================================
  Files          83       83           
  Lines        4840     4841    +1     
=======================================
+ Hits         4302     4303    +1     
  Misses        538      538           

Files Changed	Coverage Δ
lib/YaoBlocks/src/blocktools.jl	88.42% <ø> (ø)
lib/YaoBlocks/src/autodiff/apply_back.jl	96.33% <100.00%> (ø)
lib/YaoBlocks/src/autodiff/chainrules_patch.jl	86.15% <100.00%> (+0.10%)	⬆️
lib/YaoBlocks/src/composite/kron.jl	95.34% <100.00%> (ø)

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