collectd: remove the patch scaling ping_droprate from 0-1 to 0-100

Upstream project's behaviour of reporting this data source in range 0-1
is used by at least CentOS 7 collectd 5.8.1, very likely the same
behaviour is also in widely use by other distributions.

The change is important for providing consistent experience across
collectd deployments on different environments

Ref: https://github.com/collectd/collectd/pull/3244
Signed-off-by: Yousong Zhou <yszhou4tech@gmail.com>

utils/collectd/patches/920-fix-ping-droprate.patch

@@ -1,11 +0,0 @@
---- a/src/ping.c
-+++ b/src/ping.c
-@@ -648,7 +648,7 @@ static int ping_read(void) /* {{{ */
-                             ((double)(pkg_recv * (pkg_recv - 1))));
- 
-     /* Calculate drop rate. */
--    droprate = ((double)(pkg_sent - pkg_recv)) / ((double)pkg_sent);
-+    droprate = ((double)(pkg_sent - pkg_recv)) * 100 / ((double)pkg_sent);
- 
-     submit(hl->host, "ping", latency_average);
-     submit(hl->host, "ping_stddev", latency_stddev);