Revert "Export symbols needed by the Chromium component build (part 1)."

This reverts commit 9e24dcff167c4eb3555bf0ce6eaba090c10fbe53.

Reason for revert: Breaks chromium.webrtc.fyi bots.

Original change's description:
> Export symbols needed by the Chromium component build (part 1).
> 
> This CL uses RTC_EXPORT (defined in rtc_base/system/rtc_export.h)
> to mark WebRTC symbols as visible from a shared library, this doesn't
> mean these symbols are part of the public API (please continue to refer
> to [1] for info about what is considered public WebRTC API).
> 
> [1] - https://webrtc.googlesource.com/src/+/HEAD/native-api.md
> 
> Bug: webrtc:9419
> Change-Id: I802abd32874d42d3aa5ecd3c8022e7cf5e043d99
> Reviewed-on: https://webrtc-review.googlesource.com/c/103505
> Commit-Queue: Mirko Bonadei <mbonadei@webrtc.org>
> Reviewed-by: Niels Moller <nisse@webrtc.org>
> Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
> Cr-Commit-Position: refs/heads/master@{#24969}

TBR=mbonadei@webrtc.org,kwiberg@webrtc.org,nisse@webrtc.org

Change-Id: I01f6e18f0d2c0f0309cdaa6c943c3927e1f1f49f
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: webrtc:9419
Reviewed-on: https://webrtc-review.googlesource.com/c/103720
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Commit-Queue: Mirko Bonadei <mbonadei@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#24974}

modules/audio_processing/include/config.h

@@ -14,7 +14,6 @@
 #include <map>
 
 #include "rtc_base/constructormagic.h"
-#include "rtc_base/system/rtc_export.h"
 
 namespace webrtc {
 
@@ -58,7 +57,7 @@ enum class ConfigOptionID {
 //    config.Set<Algo1_CostFunction>(new SqrCost());
 //
 // Note: This class is thread-compatible (like STL containers).
-class RTC_EXPORT Config {
+class Config {
  public:
   // Returns the option if set or a default constructed one.
   // Callers that access options too often are encouraged to cache the result.