DOC: management: document cache_hits and cache_lookups in the CSV format

Counters for cache_hits and cache_lookups were added with commit
a1214a50 ("MINOR: cache: report the number of cache lookups and cache
hits") but not documented in management.txt.

(cherry picked from commit 34ebb5cbab1801b413750ff8eb0025210a6d0123)
Signed-off-by: Willy Tarreau <w@1wt.eu>
diff --git a/doc/management.txt b/doc/management.txt
index b4e09f6..19ca3b7 100644
--- a/doc/management.txt
+++ b/doc/management.txt
@@ -1101,6 +1101,8 @@
  83: wrew [LFBS]: cumulative number of failed header rewriting warnings
  84: connect [..BS]: cumulative number of connection establishment attempts
  85: reuse [..BS]: cumulative number of connection reuses
+ 86: cache_lookup [.FB.]: cumulative number of cache lookups
+ 87: cache_hits [.FB.]: cumulative number of cache hits
 
 
 9.2) Typed output format