fix `nestedview` docstring

[bjarthur]

the N and M are backwards in the docstring:

julia> Af=reshape(1:3*3*5, 3,3,5);

julia> size(Af)
(3, 3, 5)

julia> An=nestedview(Af,2);

julia> size(An)
(5,)

julia> size(An[1])
(3, 3)

julia> ndims(An[1])
2

[codecov[bot]]

Codecov Report

Merging #23 (a6f012d) into main (5a25550) will not change coverage. The diff coverage is n/a.

@@           Coverage Diff           @@
##             main      #23   +/-   ##
=======================================
  Coverage   95.78%   95.78%           
=======================================
  Files           7        7           
  Lines         451      451           
=======================================
  Hits          432      432           
  Misses         19       19           

Impacted Files	Coverage Δ
src/functions.jl	100.00% <ø> (ø)

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[oschulz]

Thanks @bjarthur !

[oschulz]

https://github.com/JuliaRegistries/General/pull/57680