[Cleanup] Add missing #include. Remove useless ones.

This CL is the result of running include-what-you-use tool on part
of the code base (audio target and dependencies) plus manual fixes.

bug: webrtc:8311
Change-Id: I277d281ce943c3ecc1bd45fd8d83055931743604
Reviewed-on: https://webrtc-review.googlesource.com/c/106280
Commit-Queue: Yves Gerey <yvesg@google.com>
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Reviewed-by: Patrik Höglund <phoglund@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#25311}
diff --git a/rtc_base/sslfingerprint.h b/rtc_base/sslfingerprint.h
index b8109e8..ea10ede 100644
--- a/rtc_base/sslfingerprint.h
+++ b/rtc_base/sslfingerprint.h
@@ -11,15 +11,17 @@
 #ifndef RTC_BASE_SSLFINGERPRINT_H_
 #define RTC_BASE_SSLFINGERPRINT_H_
 
+#include <stddef.h>
+#include <stdint.h>
 #include <string>
 
 #include "rtc_base/copyonwritebuffer.h"
-#include "rtc_base/rtccertificate.h"
-#include "rtc_base/sslidentity.h"
 
 namespace rtc {
 
+class RTCCertificate;
 class SSLCertificate;
+class SSLIdentity;
 
 struct SSLFingerprint {
   // TODO(steveanton): Remove once downstream projects have moved off of this.