package/flot: update hash

Upstream apparently updated their tarball
http://thread.gmane.org/gmane.comp.lib.uclibc.buildroot/122226/focus=138335

Issue reported upstream: https://github.com/flot/flot/issues/1484



Signed-off-by: Bernd Kuhls <bernd.kuhls@t-online.de>
Acked-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>