testing/belcard: Fix linphonec's complaint about missing vcard_grammar

Status Job ID Name Coverage
  Lint
passed #167786
x86_64 docker-alpine
lint

00:00:26

 
  Build
passed #167791
aarch64 ci-build docker-alpine
build-aarch64

00:00:57

passed #167792
armv7 ci-build docker-alpine
build-armv7

00:01:02

passed #167790
ppc64le ci-build docker-alpine
build-ppc64le

00:01:13

passed #167789
s390x ci-build docker-alpine
build-s390x

00:01:02

passed #167788
x86 ci-build docker-alpine
build-x86

00:00:41

passed #167787
x86_64 ci-build docker-alpine
build-x86_64

00:00:39