Short time domain on long axis causes repeated year labels

[jheeffer]

When you have a short time domain (e.g. 2000-2005) on more labels than 6 fix on the axis, year labels will start repeating.

https://www.gapminder.org/tools/#_state_time_value=2000&startOrigin=2000&endOrigin=2005;&marker_axis/_x_zoomedMin=2000&zoomedMax=2005;&axis/_y_which=hdi/_human/_development/_index&scaleType=linear;;;&data_/_lastModified:1526715728902&lastModified:1526715728902;&chart-type=linechart

https://www.gapminder.org/tools/#_state_time_value=2017;&marker_axis/_y_which=corruption/_perception/_index/_cpi&scaleType=linear;;;&data_/_lastModified:1526715614125&lastModified:1526715614125;&chart-type=linechart

Expected result: year labels are used max once per year, at point where the line crosses the datapoint (i.e. correct y-axis location), which seems to be the first label in the above picture.