Deprecate no-op transpose fallback instead of error'ing

[Sacha0]

Ref. #13171 and #17075. cc @tkelman @andreasnoack. Thanks!

[andreasnoack]

Should probably also add a NEWS.md entry.

[Sacha0]

Should probably also add a NEWS.md entry.

NEWS.md entry added. Thoughts? Thanks!

[tkelman]

Thoughts?

I think you rock. Should have realized it was such a simple change.

[Sacha0]

I think you rock.

Why thank you sir! 😊 Not rocking though: I should have thought to deprecate the method rather than have it throw an error the first time around. Would have saved your and others' time and energy.

Whitespace issue fixed. Thanks again!

[tkelman]

Not sure what the Travis assertion failure is about, but most likely unrelated

julia: /home/travis/build/JuliaLang/julia/src/typemap.c:862: jl_typemap_level_assoc_exact: Assertion `(((jl_value_t*)(((jl_taggedvalue_t*)((char*)(ty) - sizeof(jl_taggedvalue_t)))->header & ~(uintptr_t)15))==(jl_value_t*)(jl_datatype_type))' failed.

[Sacha0]

Thanks!

[StefanKarpinski]

Uh, this maybe should have waited a bit longer...

[StefanKarpinski]

Ah, sorry, I thought this was removing the fallback.