Remove //tools_webrtc/sancov.

While working on bugs.webrtc.org/11680 I discovered this which is
unused.

Bug: webrtc:11680
Change-Id: I43d984ee9b8a66ccc360bc24e5e1e105bc8cc049
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/177420
Reviewed-by: Artem Titov <titovartem@webrtc.org>
Commit-Queue: Mirko Bonadei <mbonadei@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#31539}

tools_webrtc/sancov/README

diff --git a/tools_webrtc/sancov/README b/tools_webrtc/sancov/README
deleted file mode 100644
index c9b43e7..0000000
--- a/tools_webrtc/sancov/README
+++ /dev/null
@@ -1,9 +0,0 @@
-Blacklist for llvm's sancov
-
-See http://clang.llvm.org/docs/SanitizerCoverage.html .
-
-Example usage:
-> cd out/Debug
-> UBSAN_OPTIONS="coverage=1" ./peerconnection_unittests
-> sancov -html-report -blacklist ../../tools/sancov/blacklist.txt \
->   peerconnection_unittests peerconnection_unittests.123.sancov

tools_webrtc/sancov/blacklist.txt

diff --git a/tools_webrtc/sancov/blacklist.txt b/tools_webrtc/sancov/blacklist.txt
deleted file mode 100644
index 7043a18..0000000
--- a/tools_webrtc/sancov/blacklist.txt
+++ /dev/null
@@ -1,21 +0,0 @@
-#############################################################################
-# sancov blacklist.
-# Please think twice before you add or remove these rules.
-
-#############################################################################
-# no coverage report for third party
-src:*/chromium/*
-src:*/third_party/*
-
-# OpenH264 triggers some errors that are out of our control.
-src:*/third_party/ffmpeg/libavcodec/*
-src:*/third_party/openh264/*
-
-#############################################################################
-# Ignore system libraries.
-src:*/usr/*
-
-#############################################################################
-# Ignore test source.
-src:*/test/*
-src:*_unittest.cc