Update svd.jl (JuliaLang#30239)

* Update svd.jl

* Update svd.jl

Make doc more useful to the reader.

* Fix grammar and one trailing whitespace

* Update svd.jl

* Fix doctests

* Avoid duplicating documentation between mutating and non-mutating
versions of svd functions.

* Reorganize generalized svd docstring and doctests

* Break some long lines

Co-authored-by: Viral B. Shah <viral@juliacomputing.com>
Co-authored-by: Andreas Noack <andreas@noack.dk>
(cherry picked from commit cec4c32)

Author: 3 people