Delete obsolete clang prebuilts.

Deleted versions:
- clang-r416183b
- clang-r450784d1
- clang-r458507
- clang-r468909b

Bug: 244341573
Test: presubmit
Change-Id: I02fe93c81cd3d3f11d9e2335fec9c3de81fb2c06
20250 files changed