remove 'alternatives' from COMMAND_WARNINGS config (#70577)

Change:
- This line causes the deprecation to make no grammatical sense. Nuking
  it.

Test Plan:
- My eyes

Signed-off-by: Rick Elrod <rick@elrod.me>

lib/ansible/config/base.yml

@@ -429,7 +429,6 @@ COMMAND_WARNINGS:
   deprecated:
     why: The command warnings feature is being removed.
     version: "2.14"
-    alternatives: N/A, these are just warnings and we no longer plan to show them.
 LOCALHOST_WARNING:
   name: Warning when using implicit inventory with only localhost
   default: True