[SYCL][DOC][P2P] Remove erroneous enum entry (#8534)

Missed an enum entry in last commit to the extension document.

Signed-off-by: James Brodman <[email protected]>

Author: jbrodman

sycl/doc/extensions/proposed/sycl_ext_oneapi_peer_access.asciidoc

@@ -101,7 +101,6 @@ namespace ext    {
 namespace oneapi {
 enum class peer_access {
   access_supported,
-  access_enabled,
   atomics_supported,
 };
 } // namespace oneapi