fix(ci): retry Go toolchain download

[mattmattox]

Completes the production verification for TaskForge #20663 after two DFW builds reached the same flaky go.dev download.

• force HTTP/1.1 for the Go tarball download
• retry transient HTTP and transport failures up to five times
• retain a 30-second connection timeout

Validation:

• downloaded the full Go 1.24.3 tarball successfully with the exact curl options (HTTP 200, 78,558,709 bytes)
• pre-push validation passed
• git diff --check passed

TaskForge: #20663