build: fix i18n usage on data/meson.build for meson 0.61.0

With the latest meson the code doesn't compile anymore and reports an error:

meld/data/meson.build:34:0: ERROR: Function does not take positional arguments.

This patch tries to fix that problem.

Close #645 (closed)

Signed-off-by: Silvio Fricke silvio.fricke@softing.com