net/ena: remove outdated devarg documentation

Removed obsolete devarg enforcing normal llq policy,
as its logic is now handled by the new `llq_policy` devarg.

Fixes: d7918d1 ("net/ena: restructure LLQ policy user setting")

Signed-off-by: Shai Brandes <shaibran@amazon.com>

doc/guides/nics/ena.rst

@@ -120,10 +120,6 @@ Runtime Configuration
 
      3 - Enforce large LLQ policy.
 
-   * **normal_llq_hdr** (default 0)
-
-     Enforce normal LLQ policy.
-
    * **miss_txc_to** (default 5)
 
      Number of seconds after which the Tx packet will be considered missing.