cmd/golangorg: update TestLiveServer for path and and date changes
cmd/golangorg: update TestLiveServer for path and and date changes

CL 296383 removed a trailing slash and .html suffix from some URLs.
CL 296429 changed the date format from yyyy/mm/dd to yyyy-mm-dd.

Update TestLiveServer accordingly so it passes on an instance that
would be deployed.

Change-Id: I6a632c8db1a6bc335946a7f6b131c6af60021b94
Reviewed-on: https://go-review.googlesource.com/c/website/+/322971
Trust: Dmitri Shuralyov <d181b7fea0ec87c86ba5a890ab716db52498e3ba@golang.org>
Reviewed-by: Russ Cox <5ad239cb8a44f659eaaee0aa1ea5b94947abe557@golang.org>

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