CLEANUP: peers: Remove unused static function `free_dcache`

The function was changed to be static in commit
6c39198b575444466ddfc5368e481d2a7cf8111d, but even that commit
no longer uses it. The purpose of the change vs. outright removal
is unclear.

see issue #301
diff --git a/src/peers.c b/src/peers.c
index e2581a7..52e2a8b 100644
--- a/src/peers.c
+++ b/src/peers.c
@@ -2890,18 +2890,6 @@
 }
 
 /*
- * Deallocate a cache of dictionary entries.
- */
-static inline void free_dcache(struct dcache *dc)
-{
-	free_dcache_tx(dc->tx);
-	dc->tx = NULL;
-	free(dc->rx); dc->rx = NULL;
-	free(dc);
-}
-
-
-/*
  * Look for the dictionary entry with the value of <i> in <d> cache of dictionary
  * entries used upon transmission.
  * Return the entry if found, NULL if not.