Delete rtc_base/unittest_main.cc

Usage replaced with test/test_main.cc.

Bug: webrtc:5996
Change-Id: I65e7539f2072fb45255a3c1af0b10dd06e1701ca
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/137805
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Reviewed-by: Tommi <tommi@webrtc.org>
Commit-Queue: Niels Moller <nisse@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#28010}
diff --git a/BUILD.gn b/BUILD.gn
index 95d7c30..4acda15 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -484,7 +484,6 @@
       "p2p:libstunprober_unittests",
       "p2p:rtc_p2p_unittests",
       "rtc_base:rtc_base_approved_unittests",
-      "rtc_base:rtc_base_tests_main",
       "rtc_base:rtc_base_unittests",
       "rtc_base:rtc_json_unittests",
       "rtc_base:rtc_numerics_unittests",
@@ -495,6 +494,7 @@
       "rtc_base/synchronization:sequence_checker_unittests",
       "rtc_base/task_utils:to_queued_task_unittests",
       "sdk:sdk_tests",
+      "test:test_main",
       "test/scenario/network:network_emulation_unittests",
     ]