Merge "Remove previous toolchain versions" am: 733601e8bc

Original change: https://android-review.googlesource.com/c/platform/prebuilts/rust/+/1554837

MUST ONLY BE SUBMITTED BY AUTOMERGER

Change-Id: I6f9a6eb6ae2f7ca0591cc3b53c30a4077ec39773
tree: 80dae9b986fd7c97e11fcd484c97da37436406f0
  1. bootstrap/
  2. darwin-x86/
  3. linux-x86/
  4. tests/
  5. Android.bp
  6. OWNERS