fix: Fix typo.

docs/flight-delays.md

@@ -82,7 +82,7 @@ While 200,000 points will stress many web-based visualization tools, Mosaic does
 
 The histograms above provide a useful first-look at the data. However, to discover relations among the data we had to interactively explore. Instead of "hiding" patterns behind interactions, let's visualize relationships directly.
 
-Below we use hexagonal bins to visualize the density (number of flights) by both time of delay and arrival delay. Interactive histograms along the edges show marginal distributions for both.
+Below we use hexagonal bins to visualize the density (number of flights) by both time of day and arrival delay. Interactive histograms along the edges show marginal distributions for both.
 
 ```js
 const $scale = vg.Param.value("log");    // color scale type