Update example announcement
Update example announcement

After sending the latest release announcement, the secretary indicated
that we should not link directly to closer.cgi, but instead to Calcite's
downloads page. Changing the sample announcement will save someone else
from future announcement rejection.

julianhyde/calcite,vlsi/calcite,xhoong/incubator-calcite,datametica/calcite,jcamachor/calcite,julianhyde/calcite,julianhyde/calcite,apache/calcite,xhoong/incubator-calcite,apache/calcite,apache/calcite,julianhyde/calcite,vlsi/calcite,looker-open-source/calcite,xhoong/incubator-calcite,googleinterns/calcite,jcamachor/calcite,vlsi/calcite,looker-open-source/calcite,vlsi/calcite,jcamachor/calcite,googleinterns/calcite,vlsi/calcite,apache/calcite,googleinterns/calcite,vlsi/incubator-calcite,julianhyde/calcite,jcamachor/calcite,jcamachor/calcite,apache/calcite,xhoong/incubator-calcite,datametica/calcite,googleinterns/calcite,googleinterns/calcite,datametica/calcite,datametica/calcite,looker-open-source/calcite,looker-open-source/calcite,datametica/calcite,vlsi/incubator-calcite,datametica/calcite,looker-open-source/calcite,googleinterns/calcite,looker-open-source/calcite,jcamachor/calcite,julianhyde/calcite,vlsi/calcite,apache/calcite