CLEANUP: fix a misspell in tests/filltab25.c

The commit fixes a misspell in a comment of tests/filltab25.c.
diff --git a/tests/filltab25.c b/tests/filltab25.c
index c57f420..3bedf25 100644
--- a/tests/filltab25.c
+++ b/tests/filltab25.c
@@ -2,7 +2,7 @@
  * experimental weighted round robin scheduler - (c) 2007 willy tarreau.
  *
  * This filling algorithm is excellent at spreading the servers, as it also
- * takes care of keeping the most uniform distance between occurences of each
+ * takes care of keeping the most uniform distance between occurrences of each
  * server, by maximizing this distance. It reduces the number of variables
  * and expensive operations.
  */