cmd/tip: remove ability to serve talks.golang.org

The tip server is primarily about serving tip.golang.org, and it does
today. There was also a time it was used to serve talks.golang.org
with an auto-deploy feature, but that ability has degraded over time
and is currently unused.

After some investigation of our options, we made a decision in issue
golang.org/issue/36825 to remove this broken and unused functionality
in favor of x/talks' own simpler App Engine deployment. If needed,
this can all be brought back and restored as part of future work,
but it's better to delete code and a misleading README until then.

Fixes golang/go#36825.
Updates golang/go#38120.

Change-Id: I5fbca48dea13e871cd04e23b36c8d3acd2f8fef5
Reviewed-on: https://go-review.googlesource.com/c/build/+/290529
Trust: Dmitri Shuralyov <[email protected]>
Run-TryBot: Dmitri Shuralyov <[email protected]>
TryBot-Result: Go Bot <[email protected]>
Reviewed-by: Alexander Rakoczy <[email protected]>

Author: dmitshur

cmd/tip/README

@@ -0,0 +1,25 @@
+<!-- Auto-generated by x/build/update-readmes.go -->
+
+[![Go Reference](https://pkg.go.dev/badge/golang.org/x/build/cmd/tip.svg)](https://pkg.go.dev/golang.org/x/build/cmd/tip)
+
+# golang.org/x/build/cmd/tip
+
+Command tip is the tip.golang.org server, serving the latest HEAD straight from the Git oven.
+
+## Deployment
+
+### Staging
+
+To deploy to the staging project https://tip-staging.golang.org:
+
+```sh
+$ make deploy-staging
+```
+
+### Production
+
+To deploy to https://tip.golang.org:
+
+```sh
+$ make deploy-prod
+```

cmd/tip/README.md

@@ -46,8 +46,6 @@ func main() {
 	switch os.Getenv(k) {
 	case "golangorg":
 		b = golangorgBuilder{}
-	case "talks":
-		b = talksBuilder{}
 	default:
 		log.Fatalf("Unknown %v value: %q", k, os.Getenv(k))
 	}