DOC: config: add the missing "force-cfg-parser-pause" to the global kw index

It was documented but missing from the index, let's add it. This can be
backported to 3.1.

doc/configuration.txt

@@ -1741,6 +1741,7 @@ The following keywords are supported in the "global" section :
 
  * Debugging
    - anonkey
+   - force-cfg-parser-pause
    - quiet
    - warn-blocked-traffic-after
    - zero-warning
@@ -4830,7 +4831,6 @@ force-cfg-parser-pause <timeout>
         expose-experimental-directives
         force-cfg-parser-pause 10s
 
-
 quick-exit
   This speeds up the old process exit upon reload by skipping the releasing of
   memory objects and listeners, since all of these are reclaimed by the