fixed typo in graph.cc
fixed typo in graph.cc

allcatsarebeautiful/tmux-mem-cpu-load,thewtex/tmux-mem-cpu-load,thewtex/tmux-mem-cpu-load,thewtex/tmux-mem-cpu-load,thewtex/tmux-mem-cpu-load,allcatsarebeautiful/tmux-mem-cpu-load,allcatsarebeautiful/tmux-mem-cpu-load,allcatsarebeautiful/tmux-mem-cpu-load