Remove the HighPassFilter interface

The functionality remains unaffected.
Filter toggling is still available via webrtc::AudioProcessing::Config.
Example:
webrtc::AudioProcessing::Config config = apm.GetConfig();
// Read settings
if (config.high_pass_filter.enabled) { ... }
// Apply setting
config.high_pass_filter.enabled = true;
apm.ApplyConfig();

Bug: webrtc:9535
Change-Id: Ib4c4b04078bbb490ebdab9721b8c7811d73777a8
Reviewed-on: https://webrtc-review.googlesource.com/c/102541
Commit-Queue: Sam Zackrisson <saza@webrtc.org>
Reviewed-by: Fredrik Solenberg <solenberg@webrtc.org>
Reviewed-by: Per Åhgren <peah@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#25198}