Fix doc typo
Merge pull request #4889 from magistere/fixes

Fix typo in complex number docs
Merge branch 'master' of github.com:JuliaLang/julia
Merge branch 'master' of github.com:JuliaLang/julia
Merge branch 'master' of github.com:JuliaLang/julia
Merge branch 'master' of github.com:JuliaLang/julia