Update more Candidate type checkers to use Candidate::is_*

This is a follow up to a previous CL that removed direct dependency on
the `cricket::` string globals.

Bug: none
Change-Id: I4d839a36739fc4694ce81b72ee036e83dae580df
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/335420
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Commit-Queue: Tomas Gunnarsson <tommi@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#41623}
diff --git a/p2p/base/basic_ice_controller.cc b/p2p/base/basic_ice_controller.cc
index 182845c..f5b3eca 100644
--- a/p2p/base/basic_ice_controller.cc
+++ b/p2p/base/basic_ice_controller.cc
@@ -16,8 +16,8 @@
 const int kMinImprovement = 10;
 
 bool IsRelayRelay(const cricket::Connection* conn) {
-  return conn->local_candidate().type() == cricket::RELAY_PORT_TYPE &&
-         conn->remote_candidate().type() == cricket::RELAY_PORT_TYPE;
+  return conn->local_candidate().is_relay() &&
+         conn->remote_candidate().is_relay();
 }
 
 bool IsUdp(const cricket::Connection* conn) {