github: fix quoting in github workflow for jitter tests

github: fix quoting in github workflow for jitter tests

Nested quoting got ignore previously. And this way one can specify
string name directly.

Successfully run with Jitter at
https://github.com/xnox/openssl/actions/runs/10223149419/job/28289017013

Reviewed-by: Neil Horman <nhorman@openssl.org>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
Reviewed-by: Tom Cosgrove <tom.cosgrove@arm.com>
(Merged from https://github.com/openssl/openssl/pull/25053)