fuzz: fix iteration comment

The fuzz test comment says each file is tested 100 times, but the
loop runs 1000 iterations. Update the comment to match the code.

libarchive/test/test_fuzz.c

@@ -31,7 +31,7 @@
  *
  * This test simply reads each archive image into memory, pokes
  * random values into it and runs it through libarchive.  It tries
- * to damage about 1% of each file and repeats the exercise 100 times
+ * to damage about 1% of each file and repeats the exercise 1000 times
  * with each file.
  *
  * Unlike most other tests, this test does not verify libarchive's