fix(deps): update go toolchain directive to v1.27.3 (#1332)

Go 1.27.3 includes a crypto/x509 security fix that distrusts a set of intermediate certificates (https://github.com/golang/go/issues/82345), so release builds need the new toolchain.

Reviewed-on: https://gitea.com/gitea/runner/pulls/1332
Reviewed-by: TheFox0x7 <95654+thefox0x7@noreply.gitea.com>

go.mod

@@ -2,7 +2,7 @@ module gitea.com/gitea/runner
 
 go 1.27
 
-toolchain go1.27.2
+toolchain go1.27.3
 
 require (
 	connectrpc.com/connect v1.21.0