DOC: cache: Use '<name>' instead of '<id>' in error message

DOC: cache: Use '<name>' instead of '<id>' in error message

When the cache name is left out in 'filter cache' the error message refers
to a missing '<id>'. The name of the cache is called 'name' within the docs.

Adjust the error message for consistency.

The error message was introduced in 99a17a2d91f9044ea20bba6617048488aed80555.
This commit first appeared in 1.9, thus the patch must be backported to 1.9+.

(cherry picked from commit ea969f6f26adfa081df0d439723813cfcd4862c4)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>
(cherry picked from commit a2acefe080df9b2430d823129173591df2c9f4a3)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>