fix(tinygo): update Go version from 1.25.0 to 1.25.3

Go 1.25.0 does not exist, causing 404 errors when downloading on all platforms:
  Error: GET returned 404 Not Found
  URL: https://go.dev/dl/go1.25.0.windows-amd64.tar.gz

Updated to Go 1.25.3 which is the current latest stable release.
This affects TinyGo's hermetic Go SDK download for all platforms.

Author: avrabe

toolchains/tinygo_toolchain.bzl

@@ -32,7 +32,7 @@ def _detect_host_platform(repository_ctx):
 def _download_go(repository_ctx, version, platform):
     """Download hermetic Go SDK for TinyGo to use"""
 
-    go_version = "1.25.0"  # Updated for TinyGo 0.39.0 support
+    go_version = "1.25.3"  # Latest stable Go version (1.25.0 doesn't exist)
 
     # Map platform to Go's naming convention
     go_platform_map = {