Delete ClearSamples helper in favor or absl::c_fill

This function doesn't add much on top a more standard function. This
function may cause a compilation failure when it is called before
defined and ArrayView is replaced with std::span as currently it works
because uses subtle argument dependent lookup rules.

Bug: webrtc:439801349
Change-Id: I0627c53594b5e9eb85446f9050dfbc5e807e25fd
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/450580
Reviewed-by: Tomas Gunnarsson <tommi@webrtc.org>
Auto-Submit: Danil Chapovalov <danilchap@webrtc.org>
Reviewed-by: Jesus de Vicente Pena <devicentepena@webrtc.org>
Commit-Queue: Tomas Gunnarsson <tommi@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#46954}