Revert "Add SSLConfig object to IceServer."

This reverts commit 7f1ffcccce563a086da037334aec2d4faa723edb.

Reason for revert: Speculative revert

Original change's description:
> Add SSLConfig object to IceServer.
> 
> This is being added to allow greater configurability to TLS connections.
> tlsAlpnProtocols, tlsEllipticCurves and tlsCertPolicy will be removed from IceServer in a
> follow-up CL.
> 
> Bug: webrtc:9662
> Change-Id: I33cb804b02c26c662ed2a28c76f9a9dc2df40f36
> Reviewed-on: https://webrtc-review.googlesource.com/96020
> Commit-Queue: Diogo Real <diogor@google.com>
> Reviewed-by: Qingsi Wang <qingsi@webrtc.org>
> Reviewed-by: Benjamin Wright <benwright@webrtc.org>
> Reviewed-by: Steve Anton <steveanton@webrtc.org>
> Reviewed-by: Sami Kalliomäki <sakal@webrtc.org>
> Reviewed-by: Kári Helgason <kthelgason@webrtc.org>
> Cr-Commit-Position: refs/heads/master@{#24559}

TBR=steveanton@webrtc.org,sakal@webrtc.org,kthelgason@webrtc.org,juberti@webrtc.org,emadomara@webrtc.org,qingsi@webrtc.org,benwright@webrtc.org,diogor@google.com

Change-Id: Iae9fc68b77f743876bda36fc2a04f6d791aae8e2
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: webrtc:9662
Reviewed-on: https://webrtc-review.googlesource.com/98000
Reviewed-by: Ying Wang <yinwa@webrtc.org>
Commit-Queue: Ying Wang <yinwa@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#24563}
diff --git a/api/peerconnectioninterface.h b/api/peerconnectioninterface.h
index c6e5a25..1c32b69 100644
--- a/api/peerconnectioninterface.h
+++ b/api/peerconnectioninterface.h
@@ -112,7 +112,6 @@
 #include "rtc_base/rtccertificate.h"
 #include "rtc_base/rtccertificategenerator.h"
 #include "rtc_base/socketaddress.h"
-#include "rtc_base/ssladapter.h"
 #include "rtc_base/sslcertificate.h"
 #include "rtc_base/sslstreamadapter.h"
 
@@ -188,7 +187,6 @@
     kIceConnectionMax,
   };
 
-  // Deprecated. TODO(diogor, webrtc:9673): Remove from API.
   // TLS certificate policy.
   enum TlsCertPolicy {
     // For TLS based protocols, ensure the connection is secure by not
@@ -213,29 +211,23 @@
     std::vector<std::string> urls;
     std::string username;
     std::string password;
-    // Deprecated. rtc::SSLConfig should be used instead.
     TlsCertPolicy tls_cert_policy = kTlsCertPolicySecure;
     // If the URIs in |urls| only contain IP addresses, this field can be used
     // to indicate the hostname, which may be necessary for TLS (using the SNI
     // extension). If |urls| itself contains the hostname, this isn't
     // necessary.
     std::string hostname;
-    // Deprecated. rtc::SSLConfig should be used instead.
     // List of protocols to be used in the TLS ALPN extension.
     std::vector<std::string> tls_alpn_protocols;
-    // Deprecated. rtc::SSLConfig should be used instead.
     // List of elliptic curves to be used in the TLS elliptic curves extension.
     std::vector<std::string> tls_elliptic_curves;
-    // SSL configuration options for any SSL/TLS connections to this IceServer.
-    rtc::SSLConfig ssl_config;
 
     bool operator==(const IceServer& o) const {
       return uri == o.uri && urls == o.urls && username == o.username &&
              password == o.password && tls_cert_policy == o.tls_cert_policy &&
              hostname == o.hostname &&
              tls_alpn_protocols == o.tls_alpn_protocols &&
-             tls_elliptic_curves == o.tls_elliptic_curves &&
-             ssl_config == o.ssl_config;
+             tls_elliptic_curves == o.tls_elliptic_curves;
     }
     bool operator!=(const IceServer& o) const { return !(*this == o); }
   };