ADFA-3771: Remove android-sdk.zip image recompression doc (#1629)

Deletes docs/process/recompress-android-sdk-images.md, added in #1602.

The runbook documents a procedure that does not belong in this repo. It
describes rewriting the locally downloaded, gitignored copies under assets/,
which is a dead end -- the published android-sdk.zip assets are built and
shipped from appdevforall/dev-assets (PR #50), so following it changes
nothing users ever download. Nothing in the repo references the file.

Docs-only; no code, build logic, or shipped asset is affected.

Author: hal-eisen-adfa