docs: fix unexported function names in svd doc

[inkydragon]

QRIteration() is not exported, so I updated the svd.jl documentation section that suggests such a method exists for the svd function. Now it says to use alg = LinearAlgebra.QRIteration() instead of alg = QRIteration() which would produce an error before.

julia> VERSION
v"1.11.2"

julia> using LinearAlgebra

julia> DivideAndConquer
ERROR: UndefVarError: `DivideAndConquer` not defined in `Main`
Suggestion: check for spelling errors or missing imports.

julia> QRIteration
ERROR: UndefVarError: `QRIteration` not defined in `Main`
Suggestion: check for spelling errors or missing imports.

julia> LinearAlgebra.DivideAndConquer
LinearAlgebra.DivideAndConquer

julia> LinearAlgebra.QRIteration
LinearAlgebra.QRIteration

Moved from JuliaLang/julia#56611

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 91.88%. Comparing base (1137b4c) to head (334a928).
Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1151      +/-   ##
==========================================
+ Coverage   91.81%   91.88%   +0.07%     
==========================================
  Files          34       34              
  Lines       15342    15339       -3     
==========================================
+ Hits        14087    14095       +8     
+ Misses       1255     1244      -11     

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