story #7511: Fix language for milestone dates

Change-Id: I9254fc1fe51499e9605110f1318aa4e60e8012da
Merge commit 'refs/changes/83/3283/1' of ssh://gerrit.tuleap.net:29418/tuleap into stable

* ssh://gerrit.tuleap.net:29418/tuleap:
  story #7511: Fix language for milestone dates
This is Tuleap 7.7.99.27

Change-Id: Icb1df61fb2caa2f4e08bb44677ea956fd9bc25f8