build_image too aggressive with right sizing

Regression introduced by c3d408e3c180327bfbc88e9147e25bb793071bf6

Found a case where 1 + 1/59 reduction in size based on free space
failed when right sizing an ext4 image. Reduced the math to 1 + 1/60.

Test: compile
Bug: 111302946
Change-Id: I6a0f3919e8d45d0b3e7cd558a6ad4d3799012f2c
diff --git a/tools/releasetools/build_image.py b/tools/releasetools/build_image.py
index b083ffd..74da3a1 100755
--- a/tools/releasetools/build_image.py
+++ b/tools/releasetools/build_image.py
@@ -297,7 +297,7 @@
         logger.info(
             "Not worth reducing image %d <= %d.", free_size, reserved_size)
       else:
-        size -= free_size + (free_size // 59)
+        size -= free_size + (free_size // 60)
         size += reserved_size
         if block_size <= 4096:
           size = common.RoundUpTo4K(size)