[Retrofit] Remove retrofit 1 client

[cbornet]

Retrofit 2.0.0 release is out !
So retrofit 1 client should be removed or at least deprecated.

[wing328]

@cbornet thanks for the update.

Has Retrofit team officially sunset Retrofit1.x library or they will still provide security fix or bug fix to Retrofit 1.x library?

My take is to keep the Retrofit 1.x client while developers are upgrading the SDKs to from Retrofit1 to Retrofit2.

[cbornet]

@wing328 Retrofit2 version upgrade has been done in #2479

Now remains the question of sunsetting retrofit 1.
I'm in favor of removing old library versions because of the work it takes to maintain them.

[wing328]

@cbornet thanks for the update I'll check with the Retrofit team for my question above (whether Retrofit 1.x is no longer supported)

[wing328]

@cbornet I've filed #3317 to update the wording.