Update README.md with current bot info

This change:
 1. Removes the gcc bot entry, as it's been disabled.
 2. Changes the linux version back to 16.04 since the 17.04 change was
    reverted.
 3. Adds a tsan bot entry.
 4. Clarifies that chromium bots are not part of the commit queue.

Change-Id: Ie13aa34f7460f12315995de2a33b668b1d36caa8
Reviewed-on: https://chromium-review.googlesource.com/c/openscreen/+/1769457
Reviewed-by: mark a. foltz <mfoltz@chromium.org>
Commit-Queue: mark a. foltz <mfoltz@chromium.org>
diff --git a/README.md b/README.md
index 9af236a..d429331 100644
--- a/README.md
+++ b/README.md
@@ -165,16 +165,18 @@
 openscreen uses [LUCI builders](https://ci.chromium.org/p/openscreen/builders)
 to monitor the build and test health of the library.  Current builders include:
 
-| Name                   | Arch   | OS                 | Toolchain | Build | Notes        |
-|------------------------|--------|--------------------|-----------|-------|--------------|
-| linux64_debug          | x86-64 | Linux Ubuntu 17.04 | clang     | debug | ASAN enabled |
-| linux64_debug_gcc      | x86-64 | Linux Ubuntu 17.04 | gcc       | debug | ASAN enabled |
-| mac_debug              | x86-64 | Mac OS X/Xcode     | clang     | debug | |
-| chromium_linux64_debug | x86-64 | Linux Ubuntu 17.04 | clang     | debug | built within chromium |
-| chromium_mac_debug     | x86-64 | Mac OS X/Xcode     | clang     | debug | built within chromium |
+| Name                   | Arch   | OS                 | Toolchain | Build   | Notes        |
+|------------------------|--------|--------------------|-----------|---------|--------------|
+| linux64_debug          | x86-64 | Linux Ubuntu 16.04 | clang     | debug   | ASAN enabled |
+| linux64_tsan           | x86-64 | Linux Ubuntu 16.04 | clang     | release | TSAN enabled |
+| mac_debug              | x86-64 | Mac OS X/Xcode     | clang     | debug   | |
+| chromium_linux64_debug | x86-64 | Linux Ubuntu 16.04 | clang     | debug   | built within chromium |
+| chromium_mac_debug     | x86-64 | Mac OS X/Xcode     | clang     | debug   | built within chromium |
 
-You can run a patch through the try job queue (which tests it on all builders)
-using `git cl try`, or through Gerrit (details below).
+You can run a patch through the try job queue (which tests it on all
+non-chromium builders) using `git cl try`, or through Gerrit (details below).
+The chromium builders only run as continuous-integration FYI bots, testing HEAD
+vs. HEAD.
 
 ## Submitting changes