Delete another empty block after trim data

'fields' block in source/data/locales/es_VE.txt is empty
after the data trimming. An empty block prevents locale fallback
chain from kicking in (es-VE => es-419) leading to a failure
in relative date format.

Fix trim_data.sh to remove an empty 'fields' block.

TBR=ftang@chromium.org

Bug: v8:8414
Test: v8: intl/regress-8414.js
Change-Id: Ibac63e869ab2e3320f7ec272919c49aedceccd75
Reviewed-on: https://chromium-review.googlesource.com/c/1319093


Reviewed-by: Jungshik Shin <jshin@chromium.org>