chore: stop bumping go directive, fast-track toolchain (#547)

Aligns Go version handling with the two distinct go.mod directives:

- The `go` directive is the minimum language version. Renovate leaves `depType: golang` disabled by default, so the rule that bumped it is removed and it no longer churns.
- The `toolchain` directive pins the exact build version. Renovate proposes `toolchain` updates by default, and a new rule fast-tracks them (`at any time`, no min-age).

Effect per consumer repo:

- With a `toolchain` directive: bumped to the latest Go patch immediately.
- With only a `go` directive: left untouched. Regular module updates still flow under the "Go dependencies" group, and `gomodTidy` raises the `go` directive only when an updated dependency requires it, so builds never break.

Mirrors the same change in gitea/gitea: https://github.com/go-gitea/gitea/pull/37846

---
This PR was written with the help of Claude Opus 4.7.

Reviewed-on: https://gitea.com/gitea/renovate-config/pulls/547
Reviewed-by: techknowlogick <9+techknowlogick@noreply.gitea.com>
Reviewed-by: Lunny Xiao <xiaolunwen@gmail.com>
Co-authored-by: silverwind <me@silverwind.io>
Co-committed-by: silverwind <me@silverwind.io>

go-deps.json

@@ -13,10 +13,9 @@
       "matchManagers": ["gomod"]
     },
     {
-      "description": "Bump the Go toolchain version immediately",
+      "description": "Bump the toolchain directive immediately",
       "matchManagers": ["gomod"],
-      "matchDepNames": ["go"],
-      "matchDepTypes": ["golang"],
+      "matchDepTypes": ["toolchain"],
       "rangeStrategy": "bump",
       "schedule": ["at any time"],
       "minimumReleaseAge": "0"