RESUMABLE: might be clearer to state a server processes rather than receives portions of an upload

[LPardue]

During WGLC review, @MikeBishop raise the folloing issue on https://lists.w3.org/Archives/Public/ietf-http-wg/2025JulSep/0123.html

Given the nature of delivery and buffers as connections are being dropped, it might be more accurate to say that the server "processes" rather than "receives" successful portions of the attempted upload, since some of the bytes might have been delivered and acknowledged at the transport layer, but not processed into the pending upload. Another instance where application semantics can't be inferred from transport state.