Prepare doctests for Julia v1.6

[jmert]

The JuliaLang/julia#36107 PR changed how type aliases are printed, and that has the consequence that every occurrence of a doctest that shows a static vector has changed from a summary line like

julia> CMB.Sphere.ẑ
3-element SArray{Tuple{3},Int64,1,3} with indices SOneTo(3):
...

to

julia> CMB.Sphere.ẑ
3-element SVector{3,Int64} with indices SOneTo(3):
...

The nightly CI doctests are now failing due to this change, so before 1.6 gets branched this issue will need to be sorted out.

[jmert]

Closed by 236cac3.