repos: don't test x/talks on build dashboard

The x/talks repository followed suit after x/blog and x/tour
and has been merged into x/website. CL 366177 removes all of
its moved content, leaving just a README.

Stop displaying it on the build dashboard and running post-submit
tests. Keep TryBots enabled in case a CL is sent with new Go code.

Change-Id: I8c13945b5ae04560d254ba679bf80696f44bed25
Reviewed-on: https://go-review.googlesource.com/c/build/+/366574
Trust: Dmitri Shuralyov <dmitshur@golang.org>
Run-TryBot: Dmitri Shuralyov <dmitshur@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Alexander Rakoczy <alex@golang.org>
diff --git a/repos/repos.go b/repos/repos.go
index 34fda8d..0555b4a 100644
--- a/repos/repos.go
+++ b/repos/repos.go
@@ -85,7 +85,7 @@
 	x("scratch", noDash)
 	x("sync", desc("additional concurrency primitives"))
 	x("sys", desc("packages for making system calls"))
-	x("talks")
+	x("talks", noDash)
 	x("term")
 	x("text", desc("packages for working with text"))
 	x("time", desc("additional time packages"))