docs: make --seccomp=profile.json clearer

There are not only allowed syscalls, also blocked ones or handled
differently.

[CI:DOCS]

Signed-off-by: Giuseppe Scrivano <[email protected]>

Author: giuseppe

docs/source/markdown/options/security-opt.image.md

@@ -19,4 +19,4 @@ container
 - `no-new-privileges`   : Not supported
 
 - `seccomp=unconfined` : Turn off seccomp confinement for the container
-- `seccomp=profile.json` :  White listed syscalls seccomp Json file to be used as a seccomp filter
+- `seccomp=profile.json` :  JSON file to be used as the seccomp filter for the container.