Replace deprecated std::not2 with a lambda

std::not2 is deprecated in C++17, and that starts failing on C++17 mode
of ios_simulator build. This CL replaces it with a lambda to avoid the
warning.

Bug: chromium:752720
Change-Id: Id7ef847df0fbe0c44583ef3320e06f44644de929
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/128620
Reviewed-by: Steve Anton <steveanton@webrtc.org>
Commit-Queue: Taiju Tsuiki <tzik@chromium.org>
Cr-Commit-Position: refs/heads/master@{#27198}

pc/sdp_utils.cc

@@ -51,7 +51,12 @@ bool SdpContentsAll(SdpContentPredicate pred,
 
 bool SdpContentsNone(SdpContentPredicate pred,
                      const cricket::SessionDescription* desc) {
-  return SdpContentsAll(std::not2(pred), desc);
+  return SdpContentsAll(
+      [pred](const cricket::ContentInfo* content_info,
+             const cricket::TransportInfo* transport_info) {
+        return !pred(content_info, transport_info);
+      },
+      desc);
 }
 
 void SdpContentsForEach(SdpContentMutator fn,