revise typo in introduction of nlyr function - 01-raster-structure.Rmd

Function is `nlyr()` but was described as `nly` in the sentence preceding the code block.

episodes/01-raster-structure.Rmd

@@ -318,7 +318,7 @@ raster: surface elevation in meters for one time period.
 
 A raster dataset can contain one or more bands. We can use the `rast()`
 function to import one single band from a single or multi-band raster. We can
-view the number of bands in a raster using the `nly()` function.
+view the number of bands in a raster using the `nlyr()` function.
 
 ```{r view-raster-bands}
 nlyr(DSM_HARV)