Update pop pyramid year and decrease burn in time

[mzimmermann-IDM]

Replace 1960 age pyramid in Kenya.py with 2015 version from the same source: [ [0, 3423916, 3389030], # Age 0 [5, 3375371, 3355162], # Age 5 [10, 2968639, 2963464], # Age 10 [15, 2489864, 2523193], # Age 15 [20, 2158196, 2218927], # Age 20 [25, 2001891, 2031898], # Age 25 [30, 1706214, 1690237], # Age 30 [35, 1366575, 1343727], # Age 35 [40, 1085439, 1080669], # Age 40 [45, 850015, 862716], # Age 45 [50, 629510, 655977], # Age 50 [55, 437712, 472329], # Age 55 [60, 280747, 317579], # Age 60 [65, 217816, 236148], # Age 65 [70, 124418, 171373], # Age 70 [75, 72579, 126721], # Age 75 [80, 44659, 80139] # Age 80 ]

[emilydriano]

fixed in PR https://github.com/fpsim/fpsim/pull/359