[release-branch.go1.25] spec: update spec date to match release date
Ths spec date in the 1.25 release branch dates back to Feb 2025
which is rather confusing. Moving it forward to 1.25 release date.
This is a roll forward of CL 709515 which was rolled back by CL 709535.
For #75743.
Fixes #75777.
Change-Id: I18d7ccfc343aa1f8fba78a896fb69ad6eeb182e7
Reviewed-on: https://go-review.googlesource.com/c/go/+/710215 Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Auto-Submit: Dmitri Shuralyov <dmitshur@google.com> Reviewed-by: Robert Griesemer <gri@google.com> Reviewed-by: Michael Pratt <mpratt@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>