go.tools/godoc/redirect: remove race detector blog post redirect

Update golang/go#7275

LGTM=minux.ma, dvyukov
R=dvyukov, minux.ma
CC=golang-codereviews
https://golang.org/cl/60900044

godoc/redirect/redirect.go

@@ -117,7 +117,6 @@ var redirects = map[string]string{
 	"/doc/articles/json_and_go.html":                 "/blog/json-and-go",
 	"/doc/articles/json_rpc_tale_of_interfaces.html": "/blog/json-rpc-tale-of-interfaces",
 	"/doc/articles/laws_of_reflection.html":          "/blog/laws-of-reflection",
-	"/doc/articles/race_detector.html":               "/blog/race-detector",
 	"/doc/articles/slices_usage_and_internals.html":  "/blog/go-slices-usage-and-internals",
 	"/doc/go_for_cpp_programmers.html":               "https://code.google.com/p/go-wiki/wiki/GoForCPPProgrammers",
 	"/doc/go_tutorial.html":                          "http://tour.golang.org/",