Reland "[cleanup] Remove useless includes."

Reason for reland: Downstream project fixed.

Original change's description:

> [cleanup] Remove useless includes.
>
> Manual cleanup guided by include-what-you-use diagnostic.
>
> Bug: webrtc:8311
> Change-Id: I00be03392cc7ee005101427ea7dc701621ccea68
> Reviewed-on: https://webrtc-review.googlesource.com/c/103320
> Commit-Queue: Yves Gerey <yvesg@webrtc.org>
> Reviewed-by: Patrik Höglund <phoglund@webrtc.org>
> Cr-Commit-Position: refs/heads/master@{#25013}

Bug: webrtc:8311
Change-Id: Id6ec4aeb798886a90ace640a190eaf16497ba31b
Reviewed-on: https://webrtc-review.googlesource.com/c/104120
Commit-Queue: Yves Gerey <yvesg@webrtc.org>
Reviewed-by: Patrik Höglund <phoglund@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#25034}
diff --git a/rtc_base/httpcommon.cc b/rtc_base/httpcommon.cc
index 716a41e..43831b7 100644
--- a/rtc_base/httpcommon.cc
+++ b/rtc_base/httpcommon.cc
@@ -18,17 +18,23 @@
 #include <security.h>
 #endif
 
+#include <ctype.h>  // for isspace
+#include <stdio.h>  // for sprintf
 #include <algorithm>
+#include <utility>  // for pair
+#include <vector>
 
 #include "rtc_base/arraysize.h"
 #include "rtc_base/checks.h"
-#include "rtc_base/cryptstring.h"
+#include "rtc_base/cryptstring.h"  // for CryptString
 #include "rtc_base/httpcommon.h"
+#include "rtc_base/logging.h"
 #include "rtc_base/messagedigest.h"
 #include "rtc_base/socketaddress.h"
 #include "rtc_base/strings/string_builder.h"
-#include "rtc_base/third_party/base64/base64.h"
-#include "rtc_base/zero_memory.h"
+#include "rtc_base/stringutils.h"                // for strcpyn, _stricmp
+#include "rtc_base/third_party/base64/base64.h"  // for Base64
+#include "rtc_base/zero_memory.h"                // for ExplicitZeroMemory
 
 namespace rtc {
 namespace {