kernelshark: fix compiling error in LatencyPlot.cpp

Include the <algorithm> header to use std::for_each.

Fixes the following compilation error:
kernel-shark/src/plugins/LatencyPlot.cpp: In function void draw_latency(kshark_cpp_argv*, int, int, int):
kernel-shark/src/plugins/LatencyPlot.cpp:306:14: error: for_each is not a member of std
  306 |         std::for_each(range.first, range.second, lamPlotLat);
      |              ^~~~~~~~

Signed-off-by: Jerome Marchand <jmarchan@redhat.com>