Remove deprecated ApacheHttpTransport

[elharo]

Only even still present for pre-Gingerbread android, which we haven't supported for years. This might moot #778

[chingor13]

We only deprecated this in May 2019, so we cannot remove this until November 2020 according to our stated policy.

[elharo]

November 2020 has passed. Let's take it out.

[stephaniewang526]

This is the preferred resolution for b/172238231.