chore: update go to 1.24.2 (#17356)

this updates `go` to the latest stable patch version `1.24.2` in:
- `go.mod`
- `dogfood/coder/Dockerfile`
- `.github/actions/setup-go/action.yaml`
- `flake.nix`

written with the assistance of ClaudeCode.

---------

Co-authored-by: Thomas Kosiewski <tk@coder.com>

flake.nix

@@ -130,7 +130,7 @@
             gnused
             gnugrep
             gnutar
-            go_1_22
+            unstablePkgs.go_1_24
             go-migrate
             (pinnedPkgs.golangci-lint)
             gopls
@@ -196,7 +196,7 @@
         # slim bundle into it's own derivation.
         buildFat =
           osArch:
-          pkgs.buildGo122Module {
+          unstablePkgs.buildGo124Module {
             name = "coder-${osArch}";
             # Updated with ./scripts/update-flake.sh`.
             # This should be updated whenever go.mod changes!