[PDF] check-jinja: Replace encrypted str w/ dummy

[PDF] check-jinja: Replace encrypted str w/ dummy

During PDF validation using `check-jinja.sh`, most if not all
encrypted strings will fail to decrypt due to missing keys on the
build server. The templater will fallback to using raw plaintext,
leading to `line too long` yamllint violations.

Since we don't care about the actual value of the unencrypted
string, replace the encrypted one with a dummy (shorter) string.

Change-Id: I0f96db0e055bf84ad43a1df4a0f2bd86cc50fd22
Signed-off-by: Alexandru Avadanii <Alexandru.Avadanii@enea.com>